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    SubjectRe: XFS vs Elevators (was Re: [PATCH RFC] nilfs2: continuous snapshotting file system)

    On Thu, 21 Aug 2008, Szabolcs Szakacsits wrote:
    > On Thu, 21 Aug 2008, Dave Chinner wrote:
    > > On Thu, Aug 21, 2008 at 04:04:18PM +1000, Dave Chinner wrote:
    > > >
    > > > One thing I just found out - my old *laptop* is 4-5x faster than the
    > > > 10krpm scsi disk behind an old cciss raid controller. I'm wondering
    > > > if the long delays in dispatch is caused by an interaction with CTQ
    > > > but I can't change it on the cciss raid controllers. Are you using
    > > > ctq/ncq on your machine?
    >
    > It's a laptop and has NCQ. It makes no difference if NCQ is enabled or
    > disabled. The problem seems to be XFS only.

    The 'nobarrier' mount option made a big improvement:

    MB/s Runtime (s)
    ----- -----------
    btrfs unstable 17.09 572
    ext3 13.24 877
    btrfs 0.16 12.33 793
    nilfs2 2nd+ runs 11.29 674
    ntfs-3g 8.55 865
    reiserfs 8.38 966
    xfs nobarrier 7.89 949
    nilfs2 1st run 4.95 3800
    xfs 1.88 3901

    Szaka

    --
    NTFS-3G: http://ntfs-3g.org


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