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    SubjectRe: very poor ext3 write performance on big filesystems?
    Andreas Dilger wrote:
    > I'm CCing the linux-raid mailing list, since I suspect they will be
    > interested in this result.
    > I would suspect that the "journal guided RAID recovery" mechanism
    > developed by U.Wisconsin may significantly benefit this workload
    > because the filesystem journal is already recording all of these
    > block numbers and the MD bitmap mechanism is pure overhead.

    Thanks for sharing these numbers. I think use of a bitmap is one of
    those things which people have to configure to match their use,
    certainly using a larger bitmap seems to reduce the delays, using an
    external bitmap certainly help, especially on an SSD. But on a large
    array, without a bitmap, performance can be compromised for hours during
    recovery, so the administrator must decide if normal case performance is
    more important than worst case performance.

    Bill Davidsen <>
    "Woe unto the statesman who makes war without a reason that will still
    be valid when the war is over..." Otto von Bismark

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