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

Szabolcs Szakacsits
2008-08-22T12:40:45Z

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