HP Surestore Disk Array 12h - And FC60, Руководство для продвинутых пользователей, Страница: 59 / 466

Disk Array High Availability Features
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Table 4
RAID Level Comparison: General Performance Characteristics
RAID Level General Performance Characteristics
RAID 0 – Simultaneous access to multiple disks increases I/O performance. In
general, the greater the number of mirrored pairs, the greater the increase
in performance.
RAID 1 – A RAID 1 mirrored pair requires one I/O operation for a read and two I/O
operations for a write, one to each disk in the pair.
– The disks in a RAID 1 mirrored pair are locked in synchronization, but the
disk array can read data from the module whose read/write heads are the
closest.
– RAID 1 read performance can be twice that of an individual disk. Write
performance can be the same as that of an individual disk.
RAID 0/1 – Simultaneous access to multiple mirrored pairs increases I/O performance.
In general, the greater the number of mirrored pairs, the greater the
increase in performance.
RAID 3 – Provides high read throughput for large sequential I/Os.
– Write performance is limited by the need to perform four I/O operations per
write request.
– Because some I/O operations occur simultaneously, performance depends
on the number of disks in the LUN. Additional disks may improve
performance.
– The I/O performance of RAID 5 benefits significantly from write caching.
RAID 5 – Provides high read throughput for small block-size requests (2 KB to 8 KB).
– Write performance is limited by the need to perform four I/O operations per
write request.
– Because some I/O operations occur simultaneously, performance depends
on the number of disks in the LUN. Additional disks may improve
performance.
– The I/O performance of RAID 5 benefits significantly from write caching.