HP Surestore Disk Array FC60 HP SureStore E Disk Array FC60 Service Manual (A5 - Page 57
Product Description, RAID Level, General Performance Characteristics
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Product Description Table 4 RAID Level Comparison: General Performance Characteristics RAID Level General Performance Characteristics RAID 0 RAID 1 RAID 0/1 RAID 3 RAID 5 - Simultaneous access to multiple disks increases I/O performance. In general, the greater the number of mirrored pairs, the greater the increase in performance. - 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. - 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. - 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 volume group. Additional disks may improve performance. - The I/O performance of RAID 5 benefits significantly from write caching. - 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 volume group. Additional disks may improve performance. - The I/O performance of RAID 5 benefits significantly from write caching. Disk Array High Availability Features 57