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

Dave Chinner
2008-08-21T08:24:20Z

On Thu, Aug 21, 2008 at 04:04:18PM +1000, Dave Chinner wrote:
> On Thu, Aug 21, 2008 at 03:15:08PM +1000, Dave Chinner wrote:
> > On Thu, Aug 21, 2008 at 05:46:00AM +0300, Szabolcs Szakacsits wrote:
> > > On Thu, 21 Aug 2008, Dave Chinner wrote:
> > > Everything is default.
> > >
> > > % rpm -qf =mkfs.xfs
> > > xfsprogs-2.9.8-7.1
> > >
> > > which, according to ftp://oss.sgi.com/projects/xfs/cmd_tars, is the
> > > latest stable mkfs.xfs. Its output is
> > >
> > > meta-data=/dev/sda8 isize=256 agcount=4, agsize=1221440 blks
> > > = sectsz=512 attr=2
> > > data = bsize=4096 blocks=4885760, imaxpct=25
> > > = sunit=0 swidth=0 blks
> > > naming =version 2 bsize=4096
> > > log =internal log bsize=4096 blocks=2560, version=2
> > > = sectsz=512 sunit=0 blks, lazy-count=0
> > > realtime =none extsz=4096 blocks=0, rtextents=0
> >
> > Ok, I thought it might be the tiny log, but it didn't improve anything
> > here when increased the log size, or the log buffer size.
>
> 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? If so, can you reduce the depth to
> something less than 4 and see what difference that makes?

Just to point out - this is not a new problem - I can reproduce
it on 2.6.24 as well as 2.6.26. Likewise, my laptop shows XFS
being faster than ext3 on both 2.6.24 and 2.6.26. So the difference
is something related to the disk subsystem on the server....

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com