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

Szabolcs Szakacsits
2008-08-23T12:48:47Z

On Fri, 22 Aug 2008, Szabolcs Szakacsits wrote:
> 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

Retested with a different disk, SATA-II, NCQ, capable of 70-110 MB/s
read/write:

MB/s Runtime (s)
----- -----------
btrfs unstable, no dup 51.42 168
btrfs unstable 42.67 197
ext4 2.6.26 35.63 245
nilfs2 2nd+ runs 26.43 287
ntfs-3g unstable 21.41 370
ext3 19.92 559
xfs nobarrier 14.17 562
reiserfs 13.11 595
nilfs2 1st run 12.06 3719
xfs nobarrier, ncq, wc off 6.89 1070
xfs 1.95 3786

Szaka

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