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Performance Tuning Guidelines for Windows Server 2003
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| bet | 16/61 | | Sana | 21.03.2017 | | Hajmi | 430.5 Kb. | | #1046 |
Most storage arrays provide some HW RAID capabilities, including the following RAID options.
Option
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Descriptoin
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RAID 0
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RAID 0 presents a logical disk that stripe disk accesses over a set of physical disks.
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Overall this is the fastest HW RAID configuration.
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This is the least expensive RAID configuration, because data is not duplicated.
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RAID 0 does not provide additional data recovery mechanisms as does RAID 1 and RAID 5.
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RAID 1
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RAID 1 presents a logical disk that is mirrored to another disk.
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RAID 1 is slower than RAID 0 for write operations, because the data needs to be written to two or more physical disks, and the latency is the slowest of the write operations.
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In some cases, RAID 1 can provide faster read operations than RAID 0 because it can read from the least busy physical disk.
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RAID 1 is the most expensive in terms of physical disks, because two or more complete copies of the data are stored.
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RAID 1 is the fastest in terms of recovery time after a physical disk failure, because the second physical disk is available for immediate use. A new mirror physical disk can be installed while full data access is permitted.
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RAID 5
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RAID 5 presents a logical disk that has parity information written to other disks as FIgure 3 shows.
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RAID 5 uses independent data disks with distributed parity blocks.
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RAID 5 is slower then RAID 0, because each logical disk write I/O results in data being written to multiple disks. However, RAID 5 provides additional data recovery capabilities over RAID 0, because data can be reconstructed from the parity.
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RAID 5 requires additional time (compared to RAID 1) to recovery from a lost physical disk, because the data on the disk needs to be rebuilt from parity information stored on other disks.
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RAID 5 is less expensive than RAID 1, because a full copy of the data is not stored on disk.
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Other
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Other combinations of RAID exist including RAID 0+1, Raid 10 and Raid 50.
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The following figure illustrates RAID 5.
Figure 3 RAID5 Overview
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