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MaxAttach NAS 6000 Administration Guide
Performance
Each of the drives is used to store the parity bit, greatly reducing any impact on
performance. This can speed small writes in multiprocessing systems. By distributing parity
across all of the array's member disks, RAID 5 reduces but does not eliminate the write
bottleneck. The performance for reads tends to be lower than for other RAID options.
The result is asymmetrical performance, with reads substantially outperforming writes.
Although arrays can be from three to 16 drives in size, longer arrays require longer write
times.
Array Size
RAID 5 can use a minimum of 3 drives and can be as large as 16 drives. In practical terms,
the optimum combination of performance and fault tolerance is usually at six drive. Larger
arrays are slower but with lower fault tolerance cost. Smaller arrays faster but are more
expensive. RAID-5 is currently viewed as the most appropriate implementation of RAID
or large systems.
Chapter #11 - Appendix - Disk Array RAID Concepts
11/07/01 -- Revision 2.0.03A
Chapter #11 - Appendix - Disk Array RAID Concepts
RAID 5 Multiple Disk Striping with Distributed Parity
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