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    SubjectRe: CFQ iosched praise: good perfomance and better latency
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    On Mon, 19 Apr 2004, Nick Piggin wrote:
    > Pedro Larroy wrote:
    >> Hi
    >> I've been trying CFQ ioscheduler in my software raid5 with nice
    >> results,
    >> I've observed that a latency pattern still exists, just as in the
    >> anticipatory ioscheduler, but those spikes are now much lower (from
    >> 6ms with AS to 2ms with CFQ as seen in the bottom of
    >> http://pedro.larroy.com/devel/iolat/analisys/),
    >> plus apps seems to get a fair amount of io so they don't get starved.
    >> Seems a good choice for io loaded boxes. Thanks Jens Axboe.
    >
    > Although AS isn't at its best when behind raid devices (it should
    > probably be in front of them), you could be seeing some problem
    > with the raid code.

    Hrm. So, if AS isn't a good to have behind RAID devices, but is
    reasonable before them, is there any easy way to configure a system like
    that?

    I don't see an easy way to change the IO scheduler on a per-device basis
    anywhere...

    Daniel


    --
    A wonderful discovery, psychoanalysis.
    Makes quite simple people feel they're complex.
    -- S. N. Behrman

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