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

Szabolcs Szakacsits
2008-08-21T17:30:02Z

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

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