dection 5Storage Devices.docx

In raid 1 were doing mirroring as we talked about

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RAID array is configured, or how the hard drives are implemented into the array. In RAID 1, we're doing mirroring, as we talked about before, if you set up mirroring, you have two hard disk drives controlled by a single RAID controller. Whenever an operation happens, the data is written to both hard drives in the exact duplicate. If one drive fails, the other drive can immediately take over and continue servicing users, providing redundancy and fault tolerance, but does not increase the speed of the system.
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RAID 5 9:00-9:41 In addition to RAID 0 and RAID 1, we can have a RAID 5 array. We may have an array that looks like this. A RAID 5 array requires a minimum of 3 disks. You can have more in the array if you want to, but you have to have a minimum of three. In RAID 5, all three of the disks are striped, which dramatically increases performance, but we reserve one portion of each disk for parity information. RAID 5 works really well, however it does have a weakness. If you do have failure in RAID 5, and one of the disks goes down, we still have parity information that can keep the array running so we can access the data. But the performance is really bad. RAID 10 9:42-10:45 RAID 10, also called RAID 1 plus 0, and sometimes RAID 1 and 0 is a stripe of mirrors. This means that a RAID 10 configuration requires a minimum of four disks, and stripes data across the mirrored pairs.As long as one disk in each mirrored pair is functional, data can be retrieved. However if two disks in the same mirrored pair fail, all data will be lost. RAID 10 provides redundancy and performance, and it is the best option for I/O intensive applications, like database, email, web servers, or any other system requiring high disk performance.One disadvantage is that only 50% of the total raw capacity of the drives is usable due to mirroring. A non-standard definition of RAID 10 was created for the Linux MD driver. Linux RAID 10 can be implemented with as few as two disks, and it offers a choice of layouts. Arrays of more than four disks are also possible. There are many other RAID levels, other than those we've talked about here. But these are the ones you should know about. Summary 10:46-10:56 In this lesson, we discussed striping, mirroring, duplexing, parity, and RAID 0, 1, 5, and 10.Implementing RAID arrays is a necessary task to maintaining and retrieving data. Redundant Array of Independent Disks (RAID), also called Redundant Array of Inexpensive Disks, is a disk subsystem that combines multiple physical disks into a single logical storage unit. Depending on the configuration, a RAID array can improve performance, provide fault tolerance, or both. The following table describes common RAID levels: RAID Level Description RAID 0 (striping) A stripe set breaks data into units and stores the units across a series of disks by reading and writing to all disks simultaneously. Striping: Provides an increase in performance Does not provide fault tolerance. A failure of one disk in the set means all data is lost.
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  • Spring '14
  • Serial ATA

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