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    SubjectRe: SATA RAID5 speed drop of 100 MB/s
    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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