Re: very unstable IOPS in the same test on the same machine

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On 01/02/2014 09:14 PM, tech8891 wrote:
Thanks for your answer, Nellans!   I think 31k IOPS should be because the RAID card cache.   Seems we have 394MB cache in this controller, which is enough hold the 2 * 128M data.

While I'm not a megaraid expert it looks like you're using 4 seagate 10k rpm drives with a 3ms random read time (looked up specs from seagat) drives in a raid 10 with a stripe size of 64KB. Raid 10 performance affects aside, you essentially have a raid-0 of two drives. At absolute best, each of your drives might be able to do 333 IOPS at a small random I/O size. 100% raid-0 efficiency would give you 666 IOPS peak. So getting 400 IOPS with random block sizes within a 1.2G range (where the disk heads don't have to move much thus speeding up seek time), seems very reasonable. Nothing seems obviously wrong to me with the performance you're seeing.
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