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Unformatted text preview: All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 11 C HAPTER Hard Drive Technologies
In this chapter, you will learn how to
• Explain how hard drives work
• Identify and explain the PATA and SATA hard drive interfaces
• Identify and explain the SCSI hard drive interfaces
• Describe how to protect data with RAID
• Install hard drives
• Configure CMOS and install drivers
• Troubleshoot hard drive installation Of all the hardware on a PC, none gets more attention—or gives more anguish—than the
hard drive. There’s a good reason for this: if the hard drive breaks, you lose data. As you
probably know, when the data goes, you have to redo work or restore from backup—or
worse. It’s good to worry about the data, because the data runs the office, maintains the
payrolls, and stores the e-mail. This level of concern is so strong that even the most neophyte PC users are exposed to terms such as IDE, PATA, SATA, and controller—even if they
don’t put the terms into practice.
This chapter focuses on how hard drives work, beginning with the internal layout
and organization of hard drives. You’ll look at the different types of hard drives used
today (PATA, SATA, SSD, and SCSI), how they interface with the PC, and how to install
them properly into a system. The chapter covers how more than one drive may work
with other drives to provide data safety and improve speed through a feature called
RAID. Let’s get started.
NOTE Chapter 12, “Implementing Hard Drives,” continues the hard drive
discussion by adding in the operating systems, showing you how to prepare
drives to receive data, and teaching you how to maintain and upgrade drives
in all versions of Windows. 397 ch11.indd 397 12/14/09 3:08:51 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 398 Historical/Conceptual
How Hard Drives Work
Hard drives sport one of two technologies today. The most common type has moving
parts; the newer and more expensive technology has none. Let’s look at both. Platter-based Hard Drives
A traditional hard disk drive (HDD) is composed of individual disks, or platters, with
read/write heads on actuator arms controlled by a servo motor—all contained in a
sealed case that prevents contamination by outside air (see Figure 11-1). Figure 11-1
hard drive The aluminum platters are coated with a magnetic medium. Two tiny read/write
heads service each platter, one to read the top and the other to read the bottom of the
platter (see Figure 11-2).
The coating on the platters is phenomenally smooth. It has to be, as the read/write
heads actually float on a cushion of air above the platters, which spin at speeds between
3500 and 10,000 rpm. The distance (flying height) between the heads and the disk ch11.indd 398 12/14/09 3:08:52 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 399 Figure 11-2
on actuator arms surface is less than the thickness of a fingerprint. The closer the read/write heads are to
the platter, the more densely the data packs onto the drive. These infinitesimal tolerances demand that the platters never be exposed to outside air. Even a tiny dust particle
on a platter would act like a mountain in the way of the read/write heads and would
cause catastrophic damage to the drive. To keep the air clean inside the drive, all hard
drives use a tiny, heavily filtered aperture to keep the air pressure equalized between the
interior and the exterior of the drive. Data Encoding
Although the hard drive stores data in binary form, visualizing a magnetized spot representing a one and a non-magnetized spot representing a zero grossly oversimplifies the
process. Hard drives store data in tiny magnetic fields—think of them as tiny magnets
that can be placed in either direction on the platter. Each tiny magnetic field, called a
flux, can switch north/south polarity back and forth through a process called flux reversal.
When a read/write head goes over an area where a flux reversal has occurred, the head
reads a small electrical current.
Today’s hard drives use a complex and efficient method to interpret flux reversals.
Instead of reading individual flux reversals, a modern hard drive reads groups of them
called runs. Starting around 1991, hard drives began using a data encoding system
known as run length limited (RLL). With RLL, any combination of ones and zeroes can
be stored in a preset combination of about 15 different runs. The hard drive looks for
these runs and reads them as a group, resulting in much faster and much more denselypacked data.
Current drives use an extremely advanced method of RLL called Partial Response Maximum Likelihood (PRML) encoding. As hard drives pack more and more fluxes on the
drive, the individual fluxes start to interact with each other, making it more and more
difficult for the drive to verify where one flux stops and another starts. PRML uses powerful, intelligent circuitry to analyze each flux reversal and to make a “best guess” as to
what type of flux reversal it just read. As a result, the maximum run length for PRML
drives reaches up to 16 to 20 fluxes, far more than the 7 or so on RLL drives. Longer run
lengths enable the hard drive to use more complicated run combinations so the hard
drive can store a phenomenal amount of data. For example, a run of only 12 fluxes on a
hard drive might equal a string of 30 or 40 ones and zeroes when handed to the system
from the hard drive. ch11.indd 399 12/14/09 3:08:52 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 400 The size required by each magnetic flux on a hard drive has reduced considerably
over the years, resulting in higher capacities. As fluxes become smaller, they begin to
interfere with each other in weird ways. I have to say weird because to make sense of
what’s going on at this subatomic level (I told you these fluxes were small!) would require you to take a semester of quantum mechanics. Let’s just say that laying fluxes flat
against the platter has reached its limit. To get around this problem, hard drive makers recently began to make hard drives that store their fluxes vertically (up and down)
rather than longitudinally (forward and backward), enabling them to make hard drives
in the 1 terabyte (1024 gigabyte) range. Manufacturers call this vertical storage method
For all this discussion and detail on data encoding, the day-to-day PC technician
never deals with encoding. Sometimes, however, knowing what you don’t need to know
helps as much as knowing what you do need to know. Fortunately, data encoding is
inherent to the hard drive and completely invisible to the system. You’re never going to
have to deal with data encoding, but you’ll sure sound smart when talking to other PC
techs if you know your RLL from your PRML! Moving the Arms
The read/write heads move across the platter on the ends of actuator arms or head actuators. In the entire history of hard drives, manufacturers have used only two technologies to move the arms: stepper motor and voice coil. Hard drives first used stepper motor
technology, but today they’ve all moved to voice coil.
Stepper motor technology moved the arm in fixed increments or steps, but the technology had several limitations that doomed it. Because the interface between motor
and actuator arm required minimal slippage to ensure precise and reproducible movements, the positioning of the arms became less precise over time. This physical deterioration caused data transfer errors. Additionally, heat deformation wreaked havoc
with stepper motor drives. Just as valve clearances in automobile engines change with
operating temperature, the positioning accuracy changed as the PC operated and various hard drive components got warmer. Although very small, these changes caused
problems. Accessing the data written on a cold hard drive, for example, became difficult
after the disk warmed. In addition, the read/write heads could damage the disk surface
if not parked (set in a non-data area) when not in use, requiring techs to use special
parking programs before transporting a stepper motor drive.
NOTE Floppy disk drives still use stepper motors. All magnetic hard drives made today employ a linear motor to move the actuator
arms. The linear motor, more popularly called a voice coil motor, uses a permanent
magnet surrounding a coil on the actuator arm. When an electrical current passes, the
coil generates a magnetic field that moves the actuator arm. The direction of the actuator arm’s movement depends on the polarity of the electrical current through the coil.
Because the voice coil and the actuator arm never touch, no degradation in positional ch11.indd 400 12/14/09 3:08:52 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 401 accuracy takes place over time. Voice coil drives automatically park the heads when the
drive loses power, making the old stepper motor park programs obsolete.
Lacking the discrete steps of the stepper motor drive, a voice coil drive cannot accurately predict the movement of the heads across the disk. To make sure voice coil drives
land exactly in the correct area, the drive reserves one side of one platter for navigational purposes. This area essentially maps the exact location of the data on the drive.
The voice coil moves the read/write head to its best guess about the correct position on
the hard drive. The read/write head then uses this map to fine-tune its true position and
make any necessary adjustments.
Now that you have a basic understanding of how a drive physically stores data, let’s
turn to how the hard drive organizes that data so we can use that drive. Geometry
Have you ever seen a cassette tape? If you look at the actual brown Mylar (a type of
plastic) tape, nothing will tell you whether sound is recorded on that tape. Assuming
the tape is not blank, however, you know something is on the tape. Cassettes store music
in distinct magnetized lines. You could say that the physical placement of those lines of
magnetism is the tape’s “geometry.”
Geometry also determines where a hard drive stores data. As with a cassette tape, if
you opened up a hard drive, you would not see the geometry. But rest assured that the
drive has geometry; in fact, every model of hard drive uses a different geometry. We describe the geometry for a particular hard drive with a set of numbers representing three
values: heads, cylinders, and sectors per track.
Heads The number of heads for a specific hard drive describes, rather logically, the
number of read/write heads used by the drive to store data. Every platter requires two
heads. If a hard drive has four platters, for example, it needs eight heads (see Figure 11-3).
Based on this description of heads, you would think that hard drives would always
have an even number of heads, right? Wrong! Most hard drives reserve a head or two
for their own use. Therefore, a hard drive can have either an even or an odd number of
Two heads per
platter Four platters = eight heads Cylinders To visualize cylinders, imagine taking an empty soup can and opening
both ends. Look at the shape of the can; it is a geometric shape called a cylinder. Now
imagine taking that cylinder and sharpening one end so that it easily cuts through the
hardest metal. Visualize placing the ex-soup can over the hard drive and pushing it down
through the drive. The can cuts into one side and out the other of each platter. Each circle
transcribed by the can is where you store data on the drive, and is called a track. ch11.indd 401 12/14/09 3:08:54 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 402 Figure 11-4
Cylinder Each side of each platter contains tens of
thousands of tracks. Interestingly enough,
the individual tracks themselves are not
directly part of the drive geometry. Our interest lies only in the groups of tracks of
the same diameter, going all of the way
through the drive. Each group of tracks
of the same diameter is a called a cylinder
(see Figure 11-4). There’s more than one
cylinder. Go get yourself about a thousand
more cans, each one a different diameter,
and push them through the hard drive. Sectors per Track Now imagine cutting the hard drive like a birthday cake, slicing all of the tracks into tens of thousands of small slivers. Each sliver then has many
thousands of small pieces of track. The term sector refers to a specific piece of track on a
sliver, and each sector stores 512 bytes of data.
The sector is the universal atom of
all hard drives. You can’t divide data
into anything smaller than a sector.
Sectors per track
Although sectors are important, the
number of sectors is not a geometry
value that describes a hard drive. The
geometry value is called sectors per
Six sectors per track
track (sectors/track). The sectors/track
value describes the number of sectors
in each track (see Figure 11-5).
The Big Three Cylinders, heads, and sectors/track combine to define the hard
drive’s geometry. In most cases, these three critical values are referred to as CHS. The
three values are important because the PC’s BIOS needs to know the drive’s geometry to
know how to talk to the drive. Back in the old days, a technician needed to enter these
values into the CMOS setup program manually. Today, every hard drive stores the CHS
information in the drive itself, in an electronic format that enables the BIOS to query
the drive automatically to determine these values. You’ll see more on this later in the
chapter, in the “Autodetection” section.
Two other values—write precompensation cylinder and landing zone—no longer
have relevance in today’s PCs; however, people still toss around these terms and a few
CMOS setup utilities still support them—another classic example of a technology appendix. Let’s look at these two holdouts from another era so when you access CMOS,
you won’t say, “What the heck are these?”
Write Precompensation Cylinder Older hard drives had a real problem with
the fact that sectors toward the inside of the drives were much smaller than sectors toward the outside. To handle this, an older drive would spread data a little farther apart
once it got to a particular cylinder. This cylinder was called the write precompensation ch11.indd 402 12/14/09 3:08:56 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 403 (write precomp) cylinder, and the PC had to know which cylinder began this wider
data spacing. Hard drives no longer have this problem, making the write precomp setting obsolete.
Landing Zone On older hard drives with stepper motors, the landing zone value
designated an unused cylinder as a “parking place” for the read/write heads. As mentioned earlier, before moving old stepper motor hard drives, the read/write heads needed
to be parked to avoid accidental damage. Today’s voice coil drives park themselves whenever they’re not accessing data, automatically placing the read/write heads on the landing
zone. As a result, the BIOS no longer needs the landing zone geometry. Essentials
Booting up a computer takes time, in part because of the time it takes for a traditional
hard drive to spin up and for the read/write heads to retrieve the data off the drive to
load the operating system and drivers into RAM. All of the moving metal parts of a
platter-based drive use a lot of power, create a lot of heat, take up space, wear down
over time, and take a lot of nanoseconds to get things done. A solid-state drive (SSD)
addresses all of these issues nicely.
In technical terms, solid-state technology and devices are based on the combination
of semiconductors, transistors, and bubble memory used to create electrical components with no moving parts. That’s a mouthful! Here’s the translation.
In simple terms, SSDs (see Figure 11-6) use memory chips to store data instead of all
those pesky metal spinning parts used in platter-based hard drives. Solid-state technology has been around for many moons. It was originally developed to transition vacuum
tube-based technologies to semiconductor technologies, such as the move from cathode
ray tubes (CRTs) to liquid crystal displays (LCDs) in monitors. (You’ll get the scoop on
monitor technologies in Chapter 19, “Video.”) Figure 11-6
drive (photo courtesy of Corsair) ch11.indd 403 12/14/09 3:08:58 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 404 NOTE With solid-state drives coming into more regular use, you see the
initials HDD used more frequently than in previous years to refer to the
traditional, platter-based hard drives. Thus we have two drive technologies:
SSDs and HDDs.
Solid-state devices use current flow and negative/positive electron charges to achieve
their magic. Although Mr. Spock may find the physics of how this technology actually
works “fascinating,” it’s more important for you to know the following points regarding solid-state drives, devices, and technology.
• Solid-state technology is commonly used in desktop and laptop hard drives,
memory cards, cameras, USB thumb drives, and other handheld devices.
• SSD form factors are typically 1.8-inch, 2.5-inch, or 3.5-inch.
• SSDs can be PATA, SATA, eSATA, SCSI, or USB for desktop systems. Some portable computers have mini-PCI Express versions.
• SSDs that use SDRAM cache are volatile and lose data when powered off. Others that use nonvolatile flash memory such as NAND retain data when power is
turned off or disconnected. (See Chapter 13, “Removable Media,” for the scoop
on flash memory technology.)
• SSDs are more expensive than traditional HDDs. Less expensive SSDs typically
implement less reliable multi-level cell (MLC) memory technology in place of
the more efficient single-level cell (SLC) technology to cut costs. Parallel and Serial ATA
Over the years, many interfaces existed for hard drives, with such names as ST-506 and
ESDI. Don’t worry about what these abbreviations stood for; neither the CompTIA
A+ certification exams nor the computer world at large has an interest in these prehistoric interfaces. Starting around 1990, an interface called advanced technology attachment
(ATA) appeared that now virtually monopolizes the hard drive market. ATA hard drives
are often referred to as integrated drive electronics (IDE) drives. Only one other type of interface, the moderately popular small computer system interface (SCSI), has any relevance
for hard drives.
NOTE The term IDE (integrated drive electronics) refers to any hard drive
with a built-in controller. All hard drives are technically IDE drives, although
we only use the term IDE when discussing ATA drives.
ATA drives come in two basic flavors. The older parallel ATA (PATA) drives send data
in parallel, on a 40- or 80-wire data cable. PATA drives dominated the industry for more
than a decade, but have been mostly replaced by serial ATA (SATA) drives that send data
in serial, using only one wire for data transfers. The leap from PATA to SATA is only
one of a large number of changes that have taken place with ATA. To appreciate these
changes, we’ll run through the many ATA standards forwarded over the years. ch11.indd 404 12/14/09 3:08:58 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 405 NOTE Modern external drives connect to a FireWire, Hi-Speed USB 2.0,
or eSATA port. All three interfaces offer high data transfer rates and hot-swap
capability, making them ideal for transporting huge files such as digital video
clips. Regardless of the external interface, however, inside the casing you’ll find
an ordinary PATA or SATA drive, just like those described in this chapter. ATA-1
When IBM unveiled the 80286-powered IBM PC AT in the early 1980s, it introduced
the first PC to include BIOS support for hard drives. This BIOS supported up to two
physical drives, and each drive could be up to 504 MB—far larger than the 5-MB and
10-MB drives of the time. Although having built-in support for hard drives certainly
improved the power of the PC, installing, configuring, and troubleshooting hard drives
could at best be called difficult at that time.
To address these problems, Western Digital and Compaq developed a new hard drive
interface and placed this specification before the American National Standards Institute
(ANSI) committees, which in turn put out the AT Attachment (ATA) interface in March
of 1989. The ATA interface specified a cable and a built-in controller on the drive itself.
Most importantly, the ATA standard used the existing AT BIOS on a PC, which meant
that you didn’t have to replace the old system BIOS to make the drive work—a very important consideration for compatibility, but one that would later haunt ATA drives. The
official name for the standard, ATA, never made it into the common vernacular until
recently, and then only as PATA to distinguish it from SATA drives.
NOTE The ANSI subcommittee directly responsible for the ATA standard is
called Technical Committee T13. If you want to know what’s happening with
ATA, check out the T13 Web site: www.t13.org. Early ATA Physical Connections
The first ATA drives connected to the computer with a 40-pin ribbon cable that plugged
into the drive and into a hard drive controller. The cable has a colored stripe down one
side that denotes pin 1 and should connect to the drive’s pin 1 and to the controller’s
pin 1. Figure 11-7 shows the business end of an early ATA drive, with the connectors for
the ribbon cable and the power cable.
Back of IDE drive
connector (right) ch11.indd 405 12/14/09 3:08:58 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 406 The controller is the support circuitry that acts as the intermediary between the hard
drive and the external data bus. Electronically, the setup looks like Figure 11-8.
Relation of drive,
bus Wait a minute! If ATA drives are IDE, they already have a built-in controller. Why
do they then have to plug into a controller on the motherboard? Well, this is a great
example of a term that’s not used properly, but everyone (including the motherboard
and hard drive makers) uses it this way. What we call the ATA controller is really no
more than an interface providing a connection to the rest of the PC system. When your
BIOS talks to the hard drive, it actually talks to the onboard circuitry on the drive, not
the connection on the motherboard. But, even though the real controller resides on the
hard drive, the 40-pin connection on the motherboard is called the controller. We have
a lot of misnomers to live with in the ATA world.
The ATA-1 standard defined that no more than two drives attach to a single IDE
connector on a single ribbon cable. Because up to two drives can attach to one connector via a single cable, you need to be able to identify each drive on the cable. The ATA
standard identifies the two drives as “master” and “slave.” You set one drive as master
and one as slave by using tiny jumpers on the drives (Figure 11-9).
A typical hard
drive with directions (top) for
setting a jumper
(bottom) The controllers are on the motherboard and manifest themselves as two 40-pin male
ports, as shown in Figure 11-10. ch11.indd 406 12/14/09 3:09:00 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 407 Figure 11-10
IDE interfaces on
a motherboard PIO and DMA Modes
If you’re making a hard drive standard, you must define both the method and the speed at
which the data’s going to move. ATA-1 defined two methods, the first using programmed
I/O (PIO) addressing and the second using direct memory access (DMA) mode.
PIO is nothing more than the traditional I/O addressing scheme, where the CPU
talks directly to the hard drive via the BIOS to send and receive data. Three different
PIO speeds called PIO modes were initially adopted:
• PIO mode 0: 3.3 MBps (megabytes per second)
• PIO mode 1: 5.2 MBps
• PIO mode 2: 8.3 MBps
DMA modes defined a method to enable the hard drives to talk to RAM directly,
using old-style DMA commands. (The ATA folks called this single-word DMA.) This
old-style DMA was slow, and the resulting three ATA single-word DMA modes were
• Single-word DMA mode 0: 2.1 MBps
• Single-word DMA mode 1: 4.2 MBps
• Single-word DMA mode 2: 8.3 MBps
When a computer booted up, the BIOS queried the hard drive to see what modes it
could use and then automatically adjusted to the fastest mode. ATA-2
In 1990, the industry adopted a series of improvements to the ATA standard called
ATA-2. Many people called these new features Enhanced IDE (EIDE). EIDE was really no
more than a marketing term invented by Western Digital, but it caught on in common
vernacular and is still used today, although its use is fading. Regular IDE drives quickly
disappeared, and by 1995, EIDE drives dominated the PC world. Figure 11-11 shows a
typical EIDE drive. ch11.indd 407 12/14/09 3:09:00 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 408 Figure 11-11
EIDE drive NOTE The terms ATA, IDE, and EIDE are used interchangeably. ATA-2 was the most important ATA standard, as it included powerful new features
such as higher capacities, support for non–hard drive storage devices, support for two
more ATA devices for a maximum of four, and substantially improved throughput. Higher Capacity with LBA
IBM created the AT BIOS to support hard drives many years before IDE drives were
invented, and every system had that BIOS. The developers of IDE made certain that the
new drives would run from the same AT BIOS command set. With this capability, you
could use the same CMOS and BIOS routines to talk to a much more advanced drive.
Your motherboard or hard drive controller wouldn’t become instantly obsolete when
you installed a new hard drive.
NOTE Hard drive makers talk about hard drive capacities in millions and
billions of bytes, not megabytes and gigabytes. Unfortunately, the BIOS routines for the original AT command set allowed a hard
drive size of only up to 528 million bytes (or 504 MB—remember that a mega =
1,048,576, not 1,000,000). A drive could have no more than 1024 cylinders, 16 heads,
and 63 sectors/track:
1024 cylinders × 16 heads × 63 sectors/track × 512 bytes/sector = 504 MB ch11.indd 408 12/14/09 3:09:00 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 409 For years, this was not a problem. But when hard drives began to approach the 504
MB barrier, it became clear that there needed to be a way of getting past 504 MB. The
ATA-2 standard defined a way to get past this limit with logical block addressing (LBA).
With LBA, the hard drive lies to the computer about its geometry through an advanced
type of sector translation. Let’s take a moment to understand sector translation, and
then come back to LBA.
Sector Translation Long before hard drives approached the 504 MB limit, the
limits of 1024 cylinders, 16 heads, and 63 sectors/track gave hard drive makers fits. The
big problem was the heads. Remember that every two heads means another platter,
another physical disk that you have to squeeze into a hard drive. If you wanted a hard
drive with the maximum number of 16 heads, you would need a hard drive with eight
physical platters inside the drive. Nobody wanted that many platters: it made the drives
too tall, it took more power to spin up the drive, and that many parts cost too much
money (see Figure 11-12).
Manufacturers could readily produce a hard drive that had fewer heads and more cylinders, but the stupid 1024/16/63 limit got in the way. Plus, the traditional sector arrangement wasted a lot of useful space. Sectors toward the inside of the drive, for example, are
much shorter than the sectors on the outside. The sectors on the outside don’t need to be
that long, but with the traditional geometry setup, hard drive makers had no choice. They
could make a hard drive store a lot more information, however, if they could make hard
drives with more sectors/track on the outside tracks (see Figure 11-13). Figure 11-12
Too many heads Figure 11-13
track ch11.indd 409 12/14/09 3:09:03 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 410 The ATA specification was designed to have two geometries. The physical geometry
defined the real layout of the CHS inside the drive. The logical geometry described what
the drive told the CMOS. In other words, the IDE drive “lied” to the CMOS, thus sidestepping the artificial limits of the BIOS. When data was being transferred to and from
the drive, the onboard circuitry of the drive translated the logical geometry into the
physical geometry. This function was, and still is, called sector translation.
Let’s look at a couple of hypothetical examples in action. First, pretend that Seagate
came out with a new, cheap, fast hard drive called the ST108. To get the ST108 drive fast
and cheap, however, Seagate had to use a rather strange geometry, shown in Table 11-1. ST108 Physical BIOS Limits Cylinders 2048 Cylinders 1024 Heads 2 Heads 16 Sectors/track 52 Sectors/track 63 Total capacity 108 MB Table 11-1 Seagate’s ST108 Drive Geometry Notice that the cylinder number is greater than 1024. To overcome this problem,
the IDE drive performs a sector translation that reports a geometry to the BIOS that
is totally different from the true geometry of the drive. Table 11-2 shows the actual
geometry and the “logical” geometry of our mythical ST108 drive. Notice that the logical geometry is now within the acceptable parameters of the BIOS limitations. Sector
translation never changes the capacity of the drive; it changes only the geometry to stay
within the BIOS limits. Physical Logical Cylinders 2048 Cylinders 512 Heads 2 Heads 8 Sectors/track 52 Sectors/track 52 Total capacity 108 MB Total capacity 108 MB Table 11-2 Physical and Logical Geometry of the ST108 Drive Back to LBA Now let’s watch how the advanced sector translation of LBA provides
support for hard drives greater than 504 MB. Let’s use an old drive, the Western Digital
WD2160, a 2.1-GB hard drive, as an example. This drive is no longer in production, but
its smaller CHS values make understanding LBA easier. Table 11-3 lists its physical and
logical geometries. ch11.indd 410 12/14/09 3:09:03 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 411 Physical Logical Cylinders 16,384 Cylinders 1024 Heads 4 Heads 64 Sectors/track 63 Sectors/track 63 Total capacity 2.1 GB Total capacity 2.1 GB Table 11-3 Western Digital WD2160’s Physical and Logical Geometries Note that, even with sector translation, the number of heads is greater than the allowed 16. So here’s where the magic of LBA comes in. The WD2160 is capable of LBA.
Now assuming that the BIOS is also capable of LBA, here’s what happens. When the
computer boots up, the BIOS asks the drives if they can perform LBA. If they say yes, the
BIOS and the drive work together to change the way they talk to each other. They can
do this without conflicting with the original AT BIOS commands by taking advantage
of unused commands to use up to 256 heads. LBA enables support for a maximum of
1024 × 256 × 63 × 512 bytes = 8.4-GB hard drives. Back in 1990, 8.4 GB was hundreds
of time larger than the drives used at the time. Don’t worry, later ATA standards will get
the BIOS up to today’s huge drives. Not Just Hard Drives Anymore: ATAPI
ATA-2 added an extension to the ATA specification, called Advanced Technology Attachment Packet Interface (ATAPI), that enabled non–hard drive devices such as CD-ROM
drives and tape backups to connect to the PC via the ATA controllers. ATAPI drives have
the same 40-pin interface and master/slave jumpers as ATA hard drives. Figure 11-14
shows an ATAPI CD-RW drive attached to a motherboard. The key difference between Figure 11-14
to a motherboard
via a standard
cable ch11.indd 411 12/14/09 3:09:04 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 412 hard drives and every other type of drive that attaches to the ATA controller is in how
the drives get BIOS support. Hard drives get it through the system BIOS, whereas non–
hard drives require the operating system to load a software driver.
NOTE With the introduction of ATAPI, the ATA standards are often
referred to as ATA/ATAPI instead of just ATA. More Drives with ATA-2
ATA-2 added support for a second controller, raising the total number of supported
drives from two to four. Each of the two controllers is equal in power and capability.
Figure 11-15 is a close-up of a typical motherboard, showing the primary controller
marked as IDE1 and the secondary marked as IDE2.
labeled on a
motherboard Increased Speed
ATA-2 defined two new PIO modes and a new type of DMA called multi-word DMA that
was a substantial improvement over the old DMA. Technically, multi-word DMA was
still the old-style DMA, but it worked in a much more efficient manner so it was much
• PIO mode 3: 11.1 MBps
• PIO mode 4: 16.6 MBps
• Multi-word DMA mode 0: 4.2 MBps
• Multi-word DMA mode 1: 13.3 MBps
• Multi-word DMA mode 2: 16.6 MBps ch11.indd 412 12/14/09 3:09:04 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 413 ATA-3
ATA-3 came on quickly after ATA-2 and added one new feature called Self-Monitoring,
Analysis, and Reporting Technology (S.M.A.R.T., one of the few PC acronyms that requires
the use of periods after each letter). S.M.A.R.T. helps predict when a hard drive is going
to fail by monitoring the hard drive’s mechanical components.
S.M.A.R.T. is a great idea and is popular in specialized server systems, but it’s complex, imperfect, and hard to understand. As a result, only a few utilities can read the
S.M.A.R.T. data on your hard drive. Your best sources are the hard drive manufacturers.
Every hard drive maker has a free diagnostic tool (which usually works only for their
drives) that will do a S.M.A.R.T. check along with other tests. Figure 11-16 shows Western Digital’s Data Lifeguard Tools in action. Note that it says only whether the drive has
passed or not. Figure 11-17 shows some S.M.A.R.T. information.
Although you can see the actual S.M.A.R.T. data, it’s generally useless or indecipherable. Your best choice is to trust the manufacturer’s opinion and run the software
Anyone who has opened a big database file on a hard drive appreciates that a faster hard drive is better. ATA-4 introduced a new DMA mode called Ultra DMA that is
now the primary way a hard drive communicates with a PC. Ultra DMA uses DMA bus
Data Lifeguard ch11.indd 413 12/14/09 3:09:05 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 414 Figure 11-17
information mastering to achieve far faster speeds than were possible with PIO or old-style DMA.
ATA-4 defined three Ultra DMA modes:
• Ultra DMA mode 0: 16.7 MBps
• Ultra DMA mode 1: 25.0 MBps
• Ultra DMA mode 2: 33.3 MBps
NOTE Ultra DMA mode 2, the most popular of the ATA-4 DMA modes,
is also called ATA/33. INT13 Extensions
Here’s an interesting factoid for you: The original ATA-1 standard allowed for hard
drives up to 137 GB. It wasn’t the ATA standard that caused the 504-MB size limit; the
standard used the old AT BIOS, and the BIOS, not the ATA standard, could support only
504 MB. LBA was a work-around that told the hard drive to lie to the BIOS to get it up
to 8.4 GB. But eventually hard drives started edging close to the LBA limit and something had to be done. The T13 folks said, “This isn’t our problem. It’s the ancient BIOS
problem. You BIOS makers need to fix the BIOS.” And they did.
In 1994, Phoenix Technologies (the BIOS manufacturer) came up with a new set
of BIOS commands called Interrupt 13 (INT13) extensions. INT13 extensions broke the
8.4-GB barrier by completely ignoring the CHS values and instead feeding the LBA a
stream of addressable sectors. A system with INT13 extensions can handle drives up to
137 GB. The entire PC industry quickly adopted INT13 extensions, and every system
made since 2000–2001 supports INT13 extensions. ch11.indd 414 12/14/09 3:09:05 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 415 ATA-5
Ultra DMA was such a huge hit that the ATA folks adopted two faster Ultra DMA modes
• Ultra DMA mode 3: 44.4 MBps
• Ultra DMA mode 4: 66.6 MBps
NOTE Ultra DMA mode 4, the most popular of the ATA-5 DMA modes, is
also called ATA/66. Ultra DMA modes 4 ran so quickly that the ATA-5 standard defined a new type of
ribbon cable that could handle the higher speeds. This 80-wire cable still has 40 pins on
the connectors, but it also includes another 40 wires in the cable that act as grounds to
improve the cable’s capability to handle high-speed signals. The 80-wire cable, just like
the 40-pin ribbon cable, has a colored stripe down one side to give you proper orientation for pin 1 on the controller and the hard drive. Previous versions of ATA didn’t define
where the various drives were plugged into the ribbon cable, but ATA-5 defined exactly
where the controller, master, and slave drives connected, even defining colors to identify them. Take a look at the ATA/66 cable in Figure 11-18. The connector on the left is
colored blue (which you could see if the photo were in color!)—and you must use that
connector to plug into the controller. The connector in the middle is grey—that’s for the
slave drive. The connector on the right is black—that’s for the master drive. Any ATA/66
controller connections are colored blue to let you know it is an ATA/66 controller. Figure 11-18
ATA/66 cable ATA/66 is backward compatible, so you may safely plug an earlier drive into an ATA/66
cable and controller. If you plug an ATA/66 drive into an older controller, it will workjust
not in ATA/66 mode. The only risky action is to use an ATA/66 controller and hard drive
with a non-ATA/66 cable. Doing so will almost certainly cause nasty data losses! ATA-6
Hard drive size exploded in the early 21st century, and the seemingly impossible-to-fill
137-GB limit created by INT13 extensions became a barrier to fine computing more
quickly than most people had anticipated. When drives started hitting the 120-GB mark, ch11.indd 415 12/14/09 3:09:05 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 416 the T13 committee adopted an industry proposal pushed by Maxtor (a major hard drive
maker) called Big Drive that increased the limit to more than 144 petabytes (approximately 144,000,000 GB). Thankfully, T13 also gave the new standard a less-silly name,
calling it ATA/ATAPI-6 or simply ATA-6. Big Drive was basically just a 48-bit LBA, supplanting the older 24-bit addressing of LBA and INT13 extensions. Plus, the standard
defined an enhanced block mode, enabling drives to transfer up to 65,536 sectors in one
chunk, up from the measly 256 sectors of lesser drive technologies.
ATA-6 also introduced Ultra DMA mode 5, kicking the data transfer rate up to 100
MBps. Ultra DMA mode 5 is more commonly referred to as ATA/100 and requires the
same 80-wire cable as ATA/66. Practical Application
ATA-7 brought two new innovations to the ATA world: one evolutionary and the other
revolutionary. The evolutionary innovation came with the last of the parallel ATA Ultra
DMA modes; the revolutionary was a new form of ATA called serial ATA (SATA).
EXAM TIP You need to know this whole chapter for the Essentials exam, so
don’t skip the rest just because of the “Practical Application” heading. ATA/133
ATA-7 introduced the fastest and probably least adopted of all of the ATA speeds, Ultra
DMA mode 6 (ATA/133). Even though it runs at a speed of 133 MBps, the fact that it
came out with SATA kept many hard drive manufacturers away. ATA/133 uses the same
cables as Ultra DMA 66 and 100.
While you won’t find many ATA/133 hard drives, you will find plenty of ATA/133
controllers. There’s a trend in the industry to color the controller connections on the
hard drive red, although this is not part of the ATA-7 standard. Serial ATA
The real story of ATA-7 is SATA. For all its longevity as the mass storage interface of
choice for the PC, parallel ATA has problems. First, the flat ribbon cables impede airflow and can be a pain to insert properly. Second, the cables have a limited length, only
18 inches. Third, you can’t hot-swap PATA drives. You have to shut down completely
before installing or replacing a drive. Finally, the technology has simply reached the
limits of what it can do in terms of throughput.
Serial ATA addresses these issues. SATA creates a point-to-point connection between
the SATA device—hard disk, CD-ROM, CD-RW, DVD-ROM, DVD-RW, BD-R, BD-RE,
and so on—and the SATA controller, the host bus adapter (HBA). At a glance, SATA devices look identical to standard PATA devices. Take a closer look at the cable and power
connectors, however, and you’ll see significant differences (Figure 11-19). ch11.indd 416 12/14/09 3:09:06 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 417 Figure 11-19
SATA hard disk
power (left) and
data (right) cables Because SATA devices send data serially instead of in parallel, the SATA interface needs
far fewer physical wires—seven instead of the eighty wires that is typical of PATA—resulting in much thinner cabling. This might not seem significant, but the benefit is
that thinner cabling means better cable control and better airflow through the PC case,
resulting in better cooling.
Further, the maximum SATA-device cable length is more than twice that of an IDE
cable—about 40 inches (1 meter) instead of 18 inches. Again, this might not seem like
a big deal unless you’ve struggled to connect a PATA hard disk installed into the top
bay of a full-tower case to an IDE connector located all the way at the bottom of the
SATA does away with the entire master/slave concept. Each drive connects to one
port, so no more daisy-chaining drives. Further, there’s no maximum number of
drivesmany motherboards are now available that support up to eight SATA drives.
Want more? Snap in a SATA HBA and load ’em up!
The big news, however, is in data throughput. As the name implies, SATA devices
transfer data in serial bursts instead of parallel, as PATA devices do. Typically, you might
not think of serial devices as being faster than parallel, but in this case, that’s exactly the
case. A SATA device’s single stream of data moves much faster than the multiple streams
of data coming from a parallel IDE device—theoretically up to 30 times faster. SATA
drives come in two common varieties, the 1.5Gb and the 3Gb, that have a maximum
throughput of 150 MBps and 300 MBps, respectively.
Number-savvy readers might have noticed a discrepancy between the names and
throughput of the two SATA drives. After all, 1.5 Gb per second throughput translates to
192 MB per second, a lot higher than the advertised speed of a “mere” 150 MBps. The
same is true of the 3Gb/300 MBps drives. The encoding scheme used on SATA drives
takes about 20 percent of the overhead for the drive, leaving 80 percent for pure bandwidth. The 3Gb drive created all kinds of problems, because the committee working on
the specifications was called the SATA II committee, and marketers picked up on the
SATA II name. As a result, you’ll find many brands called SATA II rather than 3Gb. The
SATA committee now goes by the name SATA-IO.
SATA is backward compatible with current PATA standards and enables you to install
a parallel ATA device, including a hard drive, optical drive, and other devices, to a serial
ATA controller by using a SATA bridge. A SATA bridge manifests as a tiny card that you
plug directly into the 40-pin connector on a PATA drive. As you can see in Figure 11-20, ch11.indd 417 12/14/09 3:09:07 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 418 the controller chip on the bridge requires separate power; you plug a Molex connector
into the PATA drive as normal. When you boot the system, the PATA drive shows up to
the system as a SATA drive.
SATA bridge SATA’s ease of use has made it the choice for desktop system storage, and its success
is already showing in the fact that more than 90 percent of all hard drives sold today
are SATA drives.
EXAM TIP As this book went to press, a few motherboards and hard drive
controller cards appeared that support the SATA 3.0 standard, with data
rates up to 6 GBps. Look for the SATA 3.0 drives on the store shelves after
you read this, but don’t expect the technology to be on the CompTIA A+
exams this time around.
AHCI Windows Vista and later operating systems support the Advanced Host Controller Interface (AHCI), a more efficient way to work with SATA HBAs. Using AHCI unlocks
some of the advanced features of SATA, such as hot-swapping and native command
When you plug in a SATA drive to a Windows computer that does not have AHCI enabled, the drive doesn’t appear automatically. You need to go to the Control Panel and
run the Add New Hardware Wizard to make the drive appear. AHCI makes the drive
appear in Computer, just what you’d expect from a hot-swappable device.
Native command queuing (NCQ) is a disk-optimization feature for SATA drives. It
enables faster read and write speeds.
AHCI is implemented at the CMOS level (see “BIOS Support” later in this chapter)
and generally needs to be enabled before you install the operating system. Enabling it
after installation will cause Vista to Blue Screen. Nice.
NOTE If you want to enable AHCI but you’ve already installed Windows
Vista, don’t worry! Microsoft has developed a procedure (http://support
.microsoft.com/kb/922976) that will have you enjoying all that AHCI fun in no
time. Before you jump in, note that this procedure requires you to edit your
Registry, so remember to always make a backup before you start editing. ch11.indd 418 12/14/09 3:09:07 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 419 eSATA External SATA (eSATA) extends the SATA bus to external devices, as the name
would imply. The eSATA drives use connectors similar to internal SATA, but they’re keyed
differently so you can’t mistake one for the other. Figure 11-21 shows eSATA connectors
on the back of a motherboard. External SATA uses shielded cable lengths up to 2 meters
outside the PC and is hot pluggable. The beauty of eSATA is that it extends the SATA bus
at full speed, so you’re not limited to the meager 50 or 60 MBps of FireWire or USB.
connectors If a desktop system doesn’t have an eSATA external connector, or if you need more
external SATA devices, you can install an eSATA HBA PCIe card or eSATA internal-toexternal slot plate. You can similarly upgrade laptop systems to support external SATA
devices by inserting an eSATA ExpressCard(Figure 11-22). There are also USB to eSATA
adapter plugs, although you’ll be limited to the much slower USB data-transfer rates.
Install eSATA PCIe, PC Card, or ExpressCard following the same rules and precautions
for installing any expansion device.
ExpressCard NOTE For the scoop on PC Cards and ExpressCards—both technologies
designed to add expansion options for portable computers—see Chapter 21,
“Portable Computing.” ch11.indd 419 12/14/09 3:09:08 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 420 SCSI: Still Around
Many specialized server machines and enthusiasts’ systems use the small computer system
interface (SCSI) technologies for various pieces of core hardware and peripherals, from
hard drives to printers to high-end tape-backup machines. SCSI is different from ATA in
that SCSI devices connect together in a string of devices called a chain. Each device in
the chain gets a SCSI ID to distinguish it from other devices on the chain. Last, the ends
of a SCSI chain must be terminated. Let’s dive into SCSI now, and see how SCSI chains,
SCSI IDs, and termination all work.
SCSI is an old technology dating from the late 1970s, but it has been updated continually. SCSI is faster than ATA (though the gap is closing fast), and until SATA arrived,
SCSI was the only good choice for anyone using RAID (see the “RAID” section a little
later). SCSI is arguably fading away, but it deserves some mention. SCSI Chains
SCSI manifests itself through a SCSI chain, a series of SCSI devices working together
through a host adapter. The host adapter provides the interface between the SCSI chain
and the PC. Figure 11-23 shows a typical PCI host adapter. Many techs refer to the host
adapter as the SCSI controller, so you should be comfortable with both terms. Figure 11-23
SCSI host adapter All SCSI devices can be divided into two groups: internal and external. Internal SCSI
devices are attached inside the PC and connect to the host adapter through the latter’s
internal connector. Figure 11-24 shows an internal SCSI device, in this case a CD-ROM
drive. External devices hook to the external connector of the host adapter. Figure 11-25
is an example of an external SCSI device.
Internal SCSI devices connect to the host adapter with a 68-pin ribbon cable
(Figure 11-26). This flat, flexible cable functions precisely like a PATA cable. Many external devices connect to the host adapter with a 50-pin high-density (HD) connector.
Figure 11-27 shows a host adapter external port. Higher-end SCSI devices use a 68-pin
HD connector. ch11.indd 420 12/14/09 3:09:09 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 421 Figure 11-24
CD-ROM Figure 11-25
Back of external
SCSI device Figure 11-26
ribbon cable Figure 11-27
50-pin HD port
on SCSI host
adapter ch11.indd 421 12/14/09 3:09:11 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 422 Multiple internal devices can be connected simply by using a cable with enough connectors. Figure 11-28, for example, shows a cable that can take up to four SCSI devices,
including the host adapter. Figure 11-28 Internal SCSI chain with two devices Assuming the SCSI host adapter has a standard external port (some controllers don’t
have external connections at all), plugging in an external SCSI device is as simple as
running a cable from device to controller. The external SCSI connectors are D-shaped
so you can’t plug them in backward. As an added bonus, some external SCSI devices
have two ports, one to connect to the host adapter and a second to connect to another
SCSI device. The process of connecting a device directly to another device is called daisychaining. You can daisy-chain as many as 15 devices to one host adapter. SCSI chains
can be internal, external, or both (see Figure 11-29). SCSI IDs
If you’re going to connect a number of devices on the same SCSI chain, you must
provide some way for the host adapter to tell one device from another. To differentiate devices, SCSI uses a unique identifier called the SCSI ID. The SCSI ID number can
range from 0 to 15. SCSI IDs are similar to many other PC hardware settings in that a
SCSI device can theoretically have any SCSI ID as long as that ID is not already taken by
another device connected to the same host adapter. ch11.indd 422 12/14/09 3:09:12 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 423 Figure 11-29 Internal and external devices on one SCSI chain NOTE Old SCSI equipment allowed SCSI IDs from 0 to 7 only. Some conventions should be followed when setting SCSI IDs. Typically, most people
set the host adapter to 7 or 15, but you can change this setting. Note that there is no
order for the use of SCSI IDs. It does not matter which device gets which number,
and you can skip numbers. Restrictions on IDs apply only within a single chain. Two
devices can have the same ID, in other words, as long as they are on different chains
Every SCSI device has some method of setting its SCSI ID. The trick is to figure out
how as you’re holding the device in your hand. A SCSI device may use jumpers, dip
switches, or even tiny dials; every new SCSI device is a new adventure as you try to determine how to set its SCSI ID. ch11.indd 423 12/14/09 3:09:13 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 424 Figure 11-30
IDs don’t conflict
SCSI chains. Termination
Whenever you send a signal down a wire, some of that signal reflects back up the wire,
creating an echo and causing electronic chaos. SCSI chains use termination to prevent
this problem. Termination simply means putting something on the ends of the wire to
prevent this echo. Terminators are usually pull-down resistors and can manifest themselves in many different ways. Most of the devices within a PC have the appropriate
termination built in. On other devices, including SCSI chains and some network cables,
you have to set termination during installation.
The rule with SCSI is that you must terminate only the ends of the SCSI chain. You
have to terminate the ends of the cable, which usually means that you need to terminate the two devices at the ends of the cable. Do not terminate devices that are not on
the ends of the cable. Figure 11-31 shows some examples of where to terminate SCSI
Because any SCSI device might be on the end of a chain, most manufacturers build
SCSI devices that can self-terminate. Some devices can detect that they are on the end of
the SCSI chain and automatically terminate themselves. Most devices, however, require
you to set a jumper or switch to enable termination (Figure 11-32). ch11.indd 424 12/14/09 3:09:15 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 425 Figure 11-31 Location of the terminated devices Figure 11-32
Setting termination ch11.indd 425 12/14/09 3:09:16 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 426 Protecting Data with RAID
Ask experienced techs “What is the most expensive part of a PC?” and they’ll all answer
in the same way: “It’s the data.” You can replace any single part of your PC for a few hundred dollars at most, but if you lose critical data—well, let’s just say I know of two small
companies that went out of business just because they lost a hard drive full of data.
Data is king; data is your PC’s raison d’être. Losing data is a bad thing, so you need
some method to prevent data loss. Of course, you can do backups, but if a hard drive
dies, you have to shut down the computer, reinstall a new hard drive, reinstall the operating system, and then restore the backup. There’s nothing wrong with this as long as
you can afford the time and cost of shutting down the system.
A better solution, though, would save your data if a hard drive died and enable you to
continue working throughout the process. This is possible if you stop relying on a single
hard drive and instead use two or more drives to store your data. Sounds good, but how
do you do this? Well, first of all, you could install some fancy hard drive controller that
reads and writes data to two hard drives simultaneously (Figure 11-33). The data on each
drive would always be identical. One drive would be the primary drive and the other
drive, called the mirror drive, would not be used unless the primary drive failed. This process of reading and writing data at the same time to two drives is called disk mirroring. Figure 11-33 Mirrored drives ch11.indd 426 12/14/09 3:09:20 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 427 If you really want to make data safe, you can use a separate controller for each drive.
With two drives, each on a separate controller, the system will continue to operate even
if the primary drive’s controller stops working. This super-drive mirroring technique is
called disk duplexing (Figure 11-34). Disk duplexing is also much faster than disk mirroring because one controller does not write each piece of data twice. Figure 11-34 Duplexing drives Even though duplexing is faster than mirroring, they both are slower than the classic
one-drive, one-controller setup. You can use multiple drives to increase your hard drive
access speed. Disk striping (without parity) means spreading the data among multiple
(at least two) drives. Disk striping by itself provides no redundancy. If you save a small
Microsoft Word file, for example, the file is split into multiple pieces; half of the pieces
go on one drive and half on the other (Figure 11-35).
The one and only advantage of disk striping is speed—it is a fast way to read and
write to hard drives. But if either drive fails, all data is lost. You should not do disk
striping—unless you’re willing to increase the risk of losing data to increase the speed
at which your hard drives save and restore data. ch11.indd 427 12/14/09 3:09:22 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 428 Figure 11-35 Disk striping Disk striping with parity, in contrast, protects data by adding extra information,
called parity data, that can be used to rebuild data if one of the drives fails. Disk striping with parity requires at least three drives, but it is common to use more than three.
Disk striping with parity combines the best of disk mirroring and plain disk striping.
It protects data and is quite fast. The majority of network servers use a type of disk
striping with parity. RAID
A couple of sharp guys in Berkeley back in the 1980s organized the many techniques
for using multiple drives for data protection and increasing speeds as the redundant
array of independent (or inexpensive) disks (RAID). They outlined seven levels of RAID,
numbered 0 through 6.
NOTE An array in the context of RAID refers to a collection of two or more
hard drives. ch11.indd 428 12/14/09 3:09:24 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 429 • RAID 0—Disk Striping Disk striping requires at least two drives. It does not
provide redundancy to data. If any one drive fails, all data is lost.
• RAID 1—Disk Mirroring/Duplexing RAID 1 arrays require at least two hard
drives, although they also work with any even number of drives. RAID 1 is the
ultimate in safety, but you lose storage space because the data is duplicated; you
need two 100-GB drives to store 100 GB of data.
• RAID 2—Disk Striping with Multiple Parity Drives RAID 2 was a weird
RAID idea that never saw practical use. Unused, ignore it.
• RAID 3 and 4—Disk Striping with Dedicated Parity RAID 3 and 4 combined
dedicated data drives with dedicated parity drives. The differences between the
two are trivial. Unlike RAID 2, these versions did see some use in the real world
but were quickly replaced by RAID 5.
• RAID 5—Disk Striping with Distributed Parity Instead of dedicated data and
parity drives, RAID 5 distributes data and parity information evenly across all
drives. This is the fastest way to provide data redundancy. RAID 5 is by far the
most common RAID implementation and requires at least three drives. RAID 5
arrays effectively use one drive’s worth of space for parity. If, for example, you
have three 200-GB drives, your total storage capacity is 400 GB. If you have four
200-GB drives, your total capacity is 600 GB.
• RAID 6—Disk Striping with Extra Parity If you lose a hard drive in a RAID 5
array, your data is at great risk until you replace the bad hard drive and rebuild
the array. RAID 6 is RAID 5 with extra parity information. RAID 6 needs at least
five drives, but in exchange you can lose up to two drives at the same time.
RAID 6 is gaining in popularity for those willing to use larger arrays.
NOTE No tech worth her salt says such things as “We’re implementing
disk striping with parity.” Use the RAID level. Say, “We’re implementing
RAID 5.” It’s more accurate and very impressive to the folks in the accounting
After these first RAID levels were defined, some manufacturers came up with ways
to combine different RAIDs. For example, what if you took two pairs of striped drives
and mirrored the pairs? You would get what is called RAID 0+1. Or what if (read this
carefully now) you took two pairs of mirrored drives and striped the pairs? You then get
what we call RAID 1+0 or what is often called RAID 10. Combinations of different types
of single RAID are called multiple RAID or nested RAID solutions.
NOTE There is actually a term for a storage system composed of multiple
independent disks rather than disks organized by using RAID: JBOD, which
stands for just a bunch of disks (or drives). ch11.indd 429 12/14/09 3:09:25 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 430 Implementing RAID
RAID levels describe different methods of providing data redundancy or enhancing the
speed of data throughput to and from groups of hard drives. They do not say how to
implement these methods. Literally thousands of methods can be used to set up RAID.
The method you use depends largely on the level of RAID you desire, the operating
system you use, and the thickness of your wallet.
The obvious starting place for RAID is to connect at least two hard drives in some
fashion to create a RAID array. For many years, if you wanted to do RAID beyond RAID 0
and RAID 1, the only technology you could use was good old SCSI. SCSI’s chaining of
multiple devices to a single controller made it a natural for RAID. SCSI drives make superb RAID arrays, but the high cost of SCSI drives and RAID-capable host adapters kept
RAID away from all but the most critical systems—usually big file servers.
In the past few years, substantial leaps in ATA technology have made ATA a viable
alternative to SCSI drive technology for RAID arrays. Specialized ATA RAID controller
cards support ATA RAID arrays of up to 15 drives—plenty to support even the most
complex RAID needs. In addition, the inherent hot-swap capabilities of serial ATA have
virtually guaranteed that serial ATA will quickly take over the lower end of the RAID
business. Personally, I think the price and performance of serial ATA mean SCSI’s days
Once you have a number of hard drives, the next question is whether to use hardware or software to control the array. Let’s look at both options. Hardware versus Software
All RAID implementations break down into either hardware or software methods. Software is often used when price takes priority over performance. Hardware is used when
you need speed along with data redundancy. Software RAID does not require special
controllers; you can use the regular ATA, SATA controllers, or SCSI host adapters to
make a software RAID array. But you do need “smart” software. The most common software implementation of RAID is the built-in RAID software that comes with Windows
2000, 2003, and 2008 Server. The Disk Management program in these Windows Server
versions can configure drives for RAID 0, 1, or 5, and it works with PATA, SATA, and/or
SCSI (Figure 11-36). Disk Management in Windows 2000 Professional, Windows XP,
and Windows Vista, in contrast, can only do RAID 0.
NOTE You can use Disk Management in Windows 2000, Windows XP
Professional, and Windows Vista to create RAID 1 and RAID 5 arrays, but
you can use Disk Management only remotely on a Windows 2000, 2003,
or 2008 Server OS. In other words, the capability is there, but Microsoft
has limited the OS. If you want to use software RAID in Windows 2000, XP (Home or
Professional), or Vista, you need to use a third-party tool to set it up.
Windows Disk Management is not the only software RAID game in town. A number
of third-party software programs work with Windows or other operating systems. ch11.indd 430 12/14/09 3:09:25 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 431 Figure 11-36 Disk Management tool of Computer Management in Windows 2003 Server Software RAID means the operating system is in charge of all RAID functions. It
works for small RAID solutions but tends to overwork your operating system easily,
creating slowdowns. When you really need to keep going, when you need RAID that
doesn’t even let the users know a problem has occurred, hardware RAID is the answer.
Hardware RAID centers around an intelligent controller—either a SCSI host adapter or
a PATA/SATA controller that handles all of the RAID functions (Figure 11-37). Unlike a Figure 11-37
Serial ATA RAID
controller ch11.indd 431 12/14/09 3:09:25 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 432 regular PATA/SATA controller or SCSI host adapter, these controllers have chips that have
their own processor and memory. This allows the card, instead of the operating system,
to handle all of the work of implementing RAID.
Most RAID setups in the real world are hardware-based. Almost all of the many
hardware RAID solutions provide hot-swapping—the ability to replace a bad drive without disturbing the operating system. Hot-swapping is common in hardware RAID.
Hardware-based RAID is invisible to the operating system and is configured in several ways, depending on the specific chips involved. Most RAID systems have a special
configuration utility in Flash ROM that you access after CMOS but before the OS loads.
Figure 11-38 shows a typical firmware program used to configure a hardware RAID
solution. Figure 11-38 RAID configuration utility Personal RAID
Due to drastic reductions in the cost of ATA RAID controller chips, in the past few
years we’ve seen an explosion of ATA-based hardware RAID solutions built into
mainstream motherboards. While this “ATA RAID on the motherboard” began with
parallel ATA, the introduction of serial ATA made motherboards with built-in RAID
These personal RAID motherboards might be common, but they’re not used too terribly often given that these RAID solutions usually provide only RAID 0 or RAID 1. If
you want to use RAID, spend a few extra dollars and buy a RAID 5–capable controller.
NOTE RAID controllers aren’t just for internal drives; some models can
handle multiple eSATA drives configured at any of the RAID levels. If you’re
feeling lucky, you can create a RAID array using both internal and external
SATA drives. ch11.indd 432 12/14/09 3:09:26 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 433 The Future Is RAID
RAID has been with us for about 20 years, but until only recently it was the domain
of big systems and deep pockets. During those 20 years, however, a number of factors
have come together to make RAID a reality for both big servers and common desktop
systems. Imagine a world where dirt-cheap RAID on every computer means no one ever
again losing critical data. I get goose bumps just thinking about it! Installing Drives
Installing a drive is a fairly simple process if you take the time to make sure you have
the right drive for your system, configure the drive properly, and do a few quick tests to
see if it’s running properly. Since PATA, SATA, and SCSI have different cabling requirements, we’ll look at each of these separately. Choosing Your Drive
First, decide where you’re going to put the drive. Look for an open ATA connection. Is
it PATA or SATA? Is it a dedicated RAID controller? Many motherboards with built-in
RAID controllers have a CMOS setting that enables you to turn the RAID on or off
(Figure 11-39). Figure 11-39 Settings for RAID in CMOS Second, make sure you have room for the drive in the case. Where will place it? Do
you have a spare power connector? Will the data and power cables reach the drive?
A quick test fit is always a good idea.
Don’t worry about PIO modes and DMAa new drive will support anything your
controller wants to do. ch11.indd 433 12/14/09 3:09:26 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 434 Jumpers and Cabling on PATA Drives
If you have only one hard drive, set the drive’s jumpers to master or standalone. If you
have two drives, set one to master and the other to slave. See Figure 11-40 for a close-up
of a PATA hard drive, showing the jumpers. Figure 11-40
jumpers on a
hard drive At first glance, you might notice that the jumpers aren’t actually labeled master and
slave. So how do you know how to set them properly? The easiest way is to read the
front of the drive; most drives have a diagram on housing that explains how to set the
jumpers properly. Figure 11-41 shows the front of one of these drives, so you can see
how to set the drive to master or slave.
slave settings Hard disk drives may have other jumpers that may or may not concern you during
installation. One common set of jumpers is used for diagnostics at the manufacturing
plant or for special settings in other kinds of devices that use hard drives. Ignore them;
they have no bearing in the PC world. Second, many drives provide a third setting to ch11.indd 434 12/14/09 3:09:27 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 435 be used if only one drive connects to a controller. Often, master and single drive are
the same setting on the hard drive, although some hard drives require separate settings.
Note that the name for the single drive setting varies among manufacturers. Some use
Single; others use 1 Drive or Standalone.
Many current PATA hard drives use a jumper setting called cable select rather than
master or slave. As the name implies, the position on the cable determines which drive
will be master or slave: master on the end, slave in the middle. For cable select to work
properly with two drives, you must set both drives as cable select and the cable itself
must be a special cable-select cable. If you see a ribbon cable with a pinhole through
one wire, watch out! That’s a cable-select cable.
NOTE Most of the high-speed ATA/66/100/133 cables support cable select—
try one and see!
If you don’t see a label on the drive that tells you how to set the jumpers, you have
several options. First, look for the drive maker’s Web site. Every drive manufacturer lists
its drive jumper settings on the Web, although finding the information you want can
take a while. Second, try phoning the hard drive maker directly. Unlike many other PC
parts manufacturers, hard drive producers tend to stay in business for a long time and
offer great technical support.
Hard drive cables have a colored stripe that corresponds to the number-one pin—
called pin 1—on the connector. You need to make certain that pin 1 on the controller
is on the same wire as pin 1 on the hard drive. Failing to plug in the drive properly will
also prevent the PC from recognizing the drive. If you incorrectly set the master/slave
jumpers or cable to the hard drives, you won’t break anything; it just won’t work.
Finally, you need to plug a Molex connector from the power supply into the drive.
All modern PATA drives use a Molex connector. Cabling SATA Drives
Installing SATA hard disk drives is even easier than installing PATA devices because
there’s no master, slave, or cable select configuration to mess with. In fact, there are no
jumper settings to worry about at all, as SATA supports only a single device per controller channel. Simply connect the power and plug in the controller cable as shown in
Figure 11-42—the OS automatically detects the drive and it’s ready to go. The keying on
SATA controller and power cables makes it impossible to install either incorrectly.
The biggest problem with SATA drives is that many motherboards come with four or
more. Sure, the cabling is easy enough, but what do you do when it comes time to start
the computer and the system is trying to find the right hard drive to boot up? That’s
where CMOS comes into play. Connecting Solid-state Drives
You install a solid-state drive as you would any PATA or SATA drive. Just as with earlier hard drive types, you either connect SSDs correctly and they work, or you connect ch11.indd 435 12/14/09 3:09:27 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 436 Figure 11-42
Properly connected SATA
cable them incorrectly and they don’t. If they fail, nine times out of ten they will need to be
You’re most likely to run into solid-state drives today in portable computers. SSDs
are expensive and offer a lot less storage capacity compared to traditional hard drives.
Because they require a lot less electricity to run, on the other hand, they make a lot
of sense in portable computers where battery life is the Holy Grail. You can often use
solid-state drives to replace existing platter-based drives in laptops.
Keep in mind the following considerations before installing or replacing an existing
HDD with an SSD:
• Does the system currently use a PATA or SATA interface? You need to make sure
your solid-state drive can connect properly.
• Do you have the appropriate drivers and firmware for the SSD? This is especially
important if you run Windows XP. Windows Vista, on the other hand, is likely
to load most currently implemented SSD drivers. As always, check the manufacturer’s specifications before you do anything.
• Do you have everything important backed up? Good! You are ready to turn the
system off, unplug the battery, ground yourself, and join the wonderful world of
NOTE Installing solid-state removable media such as USB thumb drives and
flash memory cards (such as SD cards) is covered in Chapter 13, “Removable
SSDs address the many shortcomings of traditional HDDs. With solid-state technology, there are no moving metal parts, less energy is used, they come in smaller form
factors, and you can access that fancy PowerPoint presentation you created and saved
almost instantaneously. In geek terms, little or no latency is involved in accessing fragmented data with solid-state devices. ch11.indd 436 12/14/09 3:09:28 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 437 EXAM TIP SSDs are more dependable as well as more expensive than
traditional hard drives. They use less energy overall, have smaller form
factors, are noiseless, and use either NAND (nonvolatile flash memory) or
SDRAM (volatile “RAM drive”) technology to store and retrieve data. They can retrieve
(read) data much faster than typical HDDs. Their write times, on the other hand, are
Don’t defragment an SSD! Because solid-state drives access data without having to
find that data on the surface of a physical disk first, there’s never any reason to defrag
one. What’s more, SSDs have a limited (albeit massive) number of read/write operations before they turn into expensive paperweights, and the defragmentation process
uses those up greedily. Connecting SCSI Drives
Connecting SCSI drives requires three things. You must use a controller that works with
your drive. You need to set unique SCSI IDs on the controller and the drive. You also
need to connect the ribbon cable and power connections properly.
With SCSI, you need to attach the data cable correctly. You can reverse a PATA cable,
for example, and nothing happens except the drive doesn’t work. If you reverse a SCSI
cable, however, you can seriously damage the drive. Just as with PATA cables, pin 1 on
the SCSI data cable must go to pin 1 on both the drive and the host adapter. BIOS Support: Configuring CMOS
and Installing Drivers
Every device in your PC needs BIOS support, and the hard drive controllers are no
exception. Motherboards provide support for the ATA hard drive controllers via the system BIOS, but they require configuration in CMOS for the specific hard drives attached.
SCSI drives require software drivers or firmware on the host adapter.
In the old days, you had to fire up CMOS and manually enter CHS information
whenever you installed a new ATA drive to ensure the system saw the drive. Today, this
process takes place, but it’s much more automated. Still, there’s plenty to do in CMOS
when you install a new hard drive.
CMOS settings for hard drives vary a lot among motherboards. The following information provides a generic look at the most common settings, but you’ll need to look at
your specific motherboard manual to understand all of the options available. Configuring Controllers
As a first step in configuring controllers, make certain they’re enabled. It’s easy to turn
off controllers in CMOS, and many motherboards turn off secondary ATA controllers
by default. Scan through your CMOS settings to locate the controller on/off options
(see Figure 11-43 for typical settings). This is also the time to check whether your onboard RAID controllers work in both RAID and non-RAID settings. ch11.indd 437 12/14/09 3:09:28 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 438 Figure 11-43 Typical controller settings in CMOS Autodetection
If the controllers are enabled and the drive is properly connected, the drive should appear in CMOS through a process called autodetection. Autodetection is a powerful and
handy feature, but it seems that every CMOS has a different way to manifest it, and how
it is manifested may affect how your computer decides which hard drive to try to boot
when you start your PC.
One of your hard drives stores the operating system needed when you boot your
computer, and your system needs a way to know where to look for this operating system. The traditional BIOS supported a maximum of only four ATA drives on two controllers, called the primary controller and the secondary controller. The BIOS looked for the
master drive on the primary controller when the system booted up. If you used only
one controller, you used the primary controller. The secondary controller was used for
CD-ROMs, DVDs, or other nonbootable drives.
Older CMOS made this clear and easy, as shown in Figure 11-44. When you booted up, the CMOS queried the drives through autodetection, and whatever drives the
CMOS saw, showed up here. In some even older CMOS, you had to run a special menu
option called Autodetect to see the drives in this screen. There are places for up to four
devices; notice that not all of them actually have a device.
The autodetection screen indicated that you installed a PATA drive correctly. If you
installed a hard drive on the primary controller as master but messed up the jumper
and set it to slave, it showed up in the autodetection screen as the slave. If you had two
drives and set them both to master, one drive or the other (or sometimes both) didn’t
appear, telling you that something was messed up in the physical installation. If you
forgot to plug in the ribbon cable or the power, the drives wouldn’t autodetect.
SATA changed the autodetection happiness. The SATA world has no such thing as master, slave, or even primary and secondary controller. To get around this, motherboards ch11.indd 438 12/14/09 3:09:28 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 439 Figure 11-44 Old standard CMOS settings with PATA and SATA today use a numbering systemand every motherboard uses its
own numbering system! One common numbering method uses the term channels for
each controller. The first boot device is channel 1, the second is channel 2, and so on.
PATA channels may have a master and a slave, but a SATA channel has only a master,
because SATA controllers support only one drive. So instead of names of drives, you see
numbers. Take a look at Figure 11-45.
Whew! Lots of hard drives! This motherboard supports the traditional four PATA
drives, and it also supports four SATA drives. Each controller is assigned a number; Figure 11-45 New standard CMOS features ch11.indd 439 12/14/09 3:09:29 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 440 note that channel 1 and channel 2 have master/slave settings, and that’s how you know
channel 1 and 2 are the PATA drives. Channels 3 through 6 are SATA, even though the
listing says master. (SATA is still somewhat new, and a CMOS using incorrect terms such
as master is common.) Boot Order
If you want your computer to run, it’s going to need an operating system to boot. While
the PCs of our forefathers (those of the 1980s and early 1990s) absolutely required you
to put the operating system on the primary master, most BIOS makers by 1995 enabled
you to put the OS on any of the four drives and then tell the system through CMOS
which hard drive to boot. With the many SATA drives available on modern systems,
you’re not even limited to a mere four choices. Additionally, you may need to boot
from an optical disc, a USB thumb drive, or even a floppy disk (if you’re feeling retro).
CMOS takes care of this by enabling you to set a boot order.
Figure 11-46 shows a typical boot-order screen, with a first, second, and third boot
option. Many users like to boot first from optical and then from a hard drive. This enables them to put in a bootable optical disc if they’re having problems with the system.
Of course, you can set it to boot first from your hard drive and then go into CMOS and
change it when you need toit’s your choice.
Boot order Most modern CMOS setup utilities lump the hard drive boot order onto a second
screen. This screen works like an autodetect in that it shows only actual hard drives
attached. This beats the heck out of guessing. Enabling AHCI
On motherboards that support AHCI, you implement it in CMOS. You’ll generally have
up to three options: IDE or compatibility mode, AHCI, or RAID. Use compatibility
mode to install older operating systems, such as Windows XP. Going to AHCI or RAID
enables the AHCI option for the HBA. Device Drivers
Devices that do not get BIOS via the system BIOS routines naturally require some
other source for BIOS. For ATAPI devices and many SATA controllers, the source of
choice is software device drivers, but both technologies have a couple of quirks you
should know about. ATAPI Devices and BIOS
ATAPI drives plug into an ATA controller on the motherboard and follow the same conventions on cabling and jumpers used by PATA hard drives. In fact, all current CMOS ch11.indd 440 12/14/09 3:09:29 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 441 setup utilities seem to autodetect optical-media ATAPI drives. If you go into CMOS after
installing a CD-ROM drive as master on the secondary IDE controller, for example, the
drive will show up just fine, as in Figure 11-47.
The reporting of installed optical-media drives in CMOS serves two purposes. First,
it tells the technician that the ATAPI drive has good connectivity. Second, it shows that
you have the option to boot to an optical disc, such as a Windows XP disc. What it
doesn’t do, however, is provide true BIOS support for that drive. That has to come with
a driver loaded at boot-up. Figure 11-47 CMOS screen showing a CD-ROM drive detected Troubleshooting Hard Drive Installation
The best friend a tech has when it comes to troubleshooting hard drive installation is
the autodetection feature of the CMOS setup utility. When a drive doesn’t work, the
biggest question, especially during installation, is “Did I plug it in correctly?” With
autodetection, the answer is simple; if the system doesn’t see the drive, something is
wrong with the hardware configuration. Either a device has physically failed or, more
likely, you didn’t give the hard drive power, plugged a cable in backward, or messed up
some other connectivity issue.
Getting a drive installed and recognized by the system takes four things: jumpers
(PATA only), data cable, power, and the CMOS setup recognizing the drive. If you miss
or mess up any of these steps, you have a drive that doesn’t exist according to the PC! To
troubleshoot hard drives, simply work your way through each step to figure out what
First, set the drive to master, slave, standalone, or cable select, depending on where
you decide to install it. If a drive is alone on the cable, set it to master or standalone. ch11.indd 441 12/14/09 3:09:29 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 442 With two drives, one must be master and the other slave. Alternatively, you can set both
drives to cable select and use a cable-select cable.
Second, you must connect the data cable to both the drive and the controller, pin 1
to pin 1. Reversing the data cable at one end is remarkably easy to do, especially with
the rounded cables. They obviously don’t have a big red stripe down the side to indicate
the location of pin 1! If you can’t autodetect the drive, check the cabling.
Third, be sure to give the hard drive power. Most hard drives use a standard Molex
connector. If you don’t hear the whirring of the drive, make certain you plugged in a
Molex from the power supply rather than from another source such as an otherwise
disconnected fan. You’d be surprised how often I’ve seen that.
Fourth, you need to provide BIOS for the controller and the drive. This can get tricky
because the typical CMOS setup program has a lot of hard drive options. Plus, you
have an added level of confusion with RAID settings and nonintegrated controllers that
require software drivers.
Once you’ve checked the physical connections, run through these issues in CMOS.
Is the controller enabled? Is the storage technology—LBA, INT13, ATA/ATAPI-6—properly set up? Similarly, can the motherboard support the type of drive you’re installing?
If not, you have a couple of options. You can flash the BIOS with an upgraded BIOS
from the manufacturer or you can get a hard drive controller that goes into an expansion slot.
Finally, with nonintegrated hard drive controllers such as those that come with many
SATA drives, make certain that you’ve installed the proper drivers for the controller.
Driver issues can crop up with new, very large drives and with changes in technology.
Always check the manufacturer’s Web site for new drivers. Beyond A+
Spindle (or Rotational) Speed
Hard drives run at a set spindle speed, measured in revolutions per minute (RPM). Older
drives run at the long-standard speed of 3600 RPM, but new drives are hitting 15,000
RPM. The faster the spindle speed, the faster the controller can store and retrieve data.
Here are the common speeds: 4500, 5400, 7200, and 10,000 RPM.
Faster drives mean better system performance, but they can also cause the computer
to overheat. This is especially true in tight cases, such as minitowers, and in cases containing many drives. Two 4500-RPM drives might run forever, snugly tucked together
in your old case. But slap a hot new 10,000 RPM drive in that same case and watch your
system start crashing right and left!
You can deal with these very fast drives by adding drive bay fans between the drives
or migrating to a more spacious case. Most enthusiasts end up doing both. Drive bay
fans sit at the front of a bay and blow air across the drive. They range in price from $10
to $100 (US) and can lower the temperature of your drives dramatically. Some cases
come with a bay fan built in (Figure 11-48). ch11.indd 442 12/14/09 3:09:29 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 443 Figure 11-48
Bay fan Airflow in a case can make or break your system stability, especially when you add
new drives that increase the ambient temperature. Hot systems get flaky and lock up at
odd moments. Many things can impede the airflow—jumbled-up ribbon cables, drives
squished together in a tiny case, fans clogged by dust or animal hair, and so on.
Technicians need to be aware of the dangers when adding a new hard drive to an
older system. Get into the habit of tying off ribbon cables, adding front fans to cases
when systems lock up intermittently, and making sure any fans run well. Finally, if a
client wants a new drive for a system in a tiny minitower with only the power supply fan
to cool it off, be gentle, but definitely steer the client to one of the slower drives! Hybrid Hard Drives
Windows Vista supports hybrid hard drives (HHDs), drives that combine flash memory and spinning platters to provide fast and reliable storage, and offers ReadyBoost
and Superfetch for faster caching and booting. Samsung has drives with 128-MB and ch11.indd 443 12/14/09 3:09:30 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 444 256-MB flash cache, for example, that shave boot times in half and, because the platters
don’t have to spin all of the time, add 20–30 minutes more of battery life for portable
computers. Adding that much more run time with only a tiny price premium and no
extra weight is the Holy Grail of portable computing. Chapter Review Questions
1. John’s system is running INT13 extensions. What is the maximum size hard
drive it can support?
A. 504 GB
B. 137 GB
C. 10 GB
D. 8.4 GB
2. How many PATA hard drives can you have on a system with two PATA hard
3. How do you differentiate two PATA drives on the same cable?
A. The flat ribbon cable has a seven-wire twist that determines which is which.
B. Set jumpers on the individual drives to determine which is master and
which is slave.
C. The PATA controller determines the hierarchy.
D. Both drives are considered equal.
4. What happens if you cable a PATA hard drive incorrectly?
A. You can destroy that hard drive.
B. The data will be erased, but the hard drive will be okay.
C. The system will not be able to communicate with that hard drive.
D. Nothing. It doesn’t matter how the cable is set up; it doesn’t have the sevenwire twist.
5. John needs to install an old ATA/100-capable hard drive to check the contents
before recycling it. Looking through his box of connectors, however, he finds
no 80-wire cable, just a 40-wire cable. If he installs the ATA/100 drive with a 40wire EIDE cable, what will happen?
A. The drive will work but will not run at the ATA/100 speed.
B. He might damage the motherboard. ch11.indd 444 12/14/09 3:09:30 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11
All-In-One Chapter 11: Hard Drive Technologies 445 C. He won’t be able to install the drive, because the cables are incompatible.
D. He will not be able to run in ATA mode.
6. What is the maximum cable length of an internal SATA device?
A. 2 meters
B. 12 inches
C. 18 inches
D. 1 meter
7. Which of the following is part of the ATA-7 standard?
A. Red controller connections on the motherboard
D. 1 meter maximum cable length
8. What is the maximum number of SATA drives you can have on a system?
A. One master, one slave
B. Two, with no master/slave distinction
D. There is no maximum other than the limitations of your motherboard.
9. Simon wants to connect his old PATA hard drive to the SATA controller in his
new computer. What does he need to do this?
A. A SATA bridge to plug into the connector on the PATA drive.
B. A PATA converter to plug into the SATA bridge on the controller.
C. Nothing at all; he can just connect the PATA drive directly to the SATA
D. He can’t do it; the SATA controller is not backward compatible with PATA
10. What do you call a series of SCSI devices working together through a host
A. A SCSI controller
B. A SCSI chain
D. Cabled SCSI Answers
1. B. A system running INT13 extensions can support up to a 137-GB hard drive.
2. D. Each controller supports two drives. ch11.indd 445 12/14/09 3:09:31 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 11 CompTIA A+Certification All-in-One Exam Guide 446 3. B. PATA drives use master/slave jumpers to differentiate between the two drives.
4. C. Nothing will be damaged or lost—there just won’t be any communication.
5. A. ATA/100 drives work fine with a 40-wire cable—they just won’t run at
6. D. The maximum cable length of an internal SATA device is 1 meter.
7. B. Serial ATA is part of the ATA-7 standard.
8. D. There is no maximum number of SATA drives you can have on a system
beyond the limits imposed by the number of ports on your motherboard/host
9. A. Simon needs a SATA bridge to plug into the connector on the PATA drive to
connect his old PATA hard drive to the SATA controller.
10. B. A series of SCSI devices working together through a host adapter is
a SCSI chain. ch11.indd 446 12/14/09 3:09:31 PM ...
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- Spring '10