chap11 - All-In-One CompTIA Network All-in-One Exam Guide...

CHAPTER
397
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 neo-
phyte 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.
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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
Inside the
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

Chapter 11: Hard Drive Technologies
399
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 toler-
ances 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