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


On Fri, 22 Aug 2008, Dave Chinner wrote:
On Thu, Aug 21, 2008 at 08:33:50PM +0300, Szabolcs Szakacsits wrote:

The 'nobarrier' mount option made a big improvement:

INteresting. Barriers make only a little difference on my laptop;
10-20% slower. But yes, barriers will have this effect on XFS.

If you've got NCQ, then you'd do better to turn off write caching
on the drive, turn off barriers and use NCQ to give you back the
performance that the write cache used to. That is, of course,
assuming the NCQ implementation doesn't suck....

Write cache off, nobarrier and AHCI NCQ lowered the XFS result:

MB/s Runtime (s)
----- -----------
btrfs unstable 17.09 572
ext3 13.24 877
btrfs 0.16 12.33 793
ntfs-3g unstable 11.52 673
nilfs2 2nd+ runs 11.29 674
reiserfs 8.38 966
xfs nobarrier 7.89 949
nilfs2 1st run 4.95 3800
xfs nobarrier, ncq, wc off 3.81 1973
xfs 1.88 3901

Szaka

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

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