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

[Szabolcs Szakacsits]

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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