Messages in this thread | | | Date | Sat, 23 Jun 2007 18:43:01 -0400 | From | Jeff Garzik <> | Subject | Re: SATA RAID5 speed drop of 100 MB/s |
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Carlo Wood wrote: > Is it possible that the measurement with "hdparm -tT" returns a higher > value for some setting, but that the over-all real-life performance > drops?
IN THEORY, RAID performance should /increase/ due to additional queued commands available to be sent to the drive. NCQ == command queueing == sending multiple commands to the drive, rather than one-at-a-time like normal.
But hdparm isn't the best test for that theory, since it does not simulate the transactions like real-world MD device usage does.
We have seen buggy NCQ firmwares where performance decreases, so it is possible that NCQ just isn't good on your drives.
Jeff
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