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| What's Wrong with Intel Matrix RAID |
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Six Port Controllers Can't Well, let me clarify that. The ICH*R controllers now generally have 6 ports for hard disks and other devices, and support port multipliers to connect up to 24 or 30 disks. The documentation says you can attach 6 disks, and I have done this so I know it works.
Except the RAID sets are limited to 4 disks.
I'm sure there is some wonderful marketing reason not to allow creation of bigger arrays but there are also fantastic technical reasons to allow them:
- RAID 5 arrays can be extremely efficient with 5 disks, because the block sizes are a multiple of 4. So the 128KB stripe of data gets converted into 4 x 32KB blocks of data and a 32KB block of parity. This is good for performance. Other good values are 3 and 9 disks.
- RAID 10 arrays would benefit from having 6 disks instead of 4. There are arguments against port multipliers for pure performance, but 12 disks would really ROCK for performance. Each disk can add around 10MB per second of data read or write when doing random operations, or around 100 operations each second. Going from 4 to 6 disks would mean performance improvements of 50% or so. 4 to 12 could approach 200% faster.
