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I have RAID controller with 24 SATA disks. Which configuration is faster?

  1. One RAID5 with all disks.
  2. Six RAIDs with 4 disks in each group.
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3 Answers

up vote 2 down vote accepted

To answer: Option 2 is faster than Option 1.

With one group of 24 discs, RAID5 will limit your writes to the speed of the one disc for parity, which is likely to become a bottleneck on any sensible activity. With 6 groups, there are obviousl 6 independent parity discs, so your write performacne theoretically is about 6 times as high.

That said, I would consider such a setup highly inefficient. There is a lot between sky and earth, so to say. I would possibly try mitigating the bad write performance through other means.

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Neither - R5'ing 24 disks is a recipe for disaster, in fact many RAID controllers won't even let you create a single R5 array with more than around 14 disks, the risk is too great. And the 6 x 4 R5's makes no sense either.

You don't mention your definition of performance but if you want the fastest configuration then R10 is the way but presumably you don't want to lose 12 disks worth of space (although the 6 x 4 would lose you 6 right), If I couldn't go for R10 then I'd go for R50 or R60, losing either 2 or 4 disks space myself.

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RAID60 in a 2x12 configuration would likely be the fastest while not losing as many disks as RAID10 (assuming a high end RAID HBA). As Robert points out, build and benchmark is the best way to know. –  Chris S Apr 25 '11 at 12:35
It's not production solution. It's just interes. Does iosp higher when I have more then one RAID group, or not? –  d_pilot Apr 28 '11 at 9:03
If this is a purely theoretical question you need to add much more detail; OS, file system, cluster and block sizes, and IO characteristics at the very least. –  Chopper3 Apr 28 '11 at 9:22
OS, file system, cluster and block sizes may be same and no affect. –  d_pilot May 5 '11 at 8:55
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As this is very dependant on the actual controller you have, the only answer is "measure them both ways and see for yourself".

With 24 spindles, I wouldn't use RAID5 myself anyway, but that's kinda besides the point.

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