RAID 5 (Striping with Single Parity)
RAID 5 uses the striping technique in combination with single parity to provide high fault tolerance. At least three physical disks are required to create a RAID 5 virtual disk/array, as shown in Figure 1. Data and parity information are striped across all physical disks, with RAID parity information requiring the equivalent of one physical disk, regardless of the number of physical disks.
Table 1 describes RAID 5 across a number of parameters.
Parameter |
Rating |
Description |
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Read Performance |
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Read performance is good (due to striping) but write performance is comparatively lower because of the need to calculate and write single parity information. |
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Write Performance |
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Fault Tolerance |
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The combination of striping and parity provides good fault tolerance with a more efficient use of physical disk space than RAID 1 (disk mirroring). A RAID 5 virtual disk/array can tolerate the failure of one physical disk. |
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Efficient use of disk capacity |
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When the minimum three physical disks are used in a RAID 5, approximately 33% of the combined disk capacity is used for redundancy (term used to describe storing of parity or mirror data). The capacity efficiency increases as the number of physical disks increases (because only one physical disk is used for redundancy irrespective of the number of physical disks). |
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Automatic rebuild |
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Available. |
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Minimum number of drives |
|
3 |
Figure 1 describes RAID 5.
Figure 2 shows a Flash® demo of RAID 5.
Note: To view the Flash® demo for RAID 5, install the latest version of Adobe Flash Player at http://get.adobe.com/flashplayer/