LSI MegaRAID Enterprise 1600 User Manual
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MegaRAID Enterprise 1600 Hardware Guide
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RAID 3,
Continued
RAID 5 vs RAID 3 You may find that RAID 5 is preferable to RAID 3 even for applications characterized by
sequential reads and writes, because MegaRAID has very robust caching algorithms and hardware
based exclusive-or assist.
The benefits of RAID 3 disappear if there are many small I/O operations scattered randomly and
widely across the disks in the logical drive. The RAID 3 fixed parity disk becomes a bottleneck in
such applications. For example: The host attempts to make two small writes and the writes are
widely scattered, involving two different stripes and different disk drives. Ideally both writes
should take place at the same time. But this is not possible in RAID 3, since the writes must take
turns accessing the fixed parity drive. For this reason, RAID 5 is the clear choice in this scenario.