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

Martin Knoblauch
2008-08-21T11:04:07Z

----- Original Message ----

> From: Dave Chinner <david@fromorbit.com>
> To: Szabolcs Szakacsits <szaka@ntfs-3g.org>; Andrew Morton <akpm@linux-foundation.org>; linux-fsdevel@vger.kernel.org; linux-kernel@vger.kernel.org; xfs@oss.sgi.com
> Sent: Thursday, August 21, 2008 10:25:32 AM
> Subject: Re: XFS vs Elevators (was Re: [PATCH RFC] nilfs2: continuous snapshotting file system)
>
> 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....
>
Hi Dave,

just curious - which CCISS controller and and what kind of disk configuration are you using.

Cheers
Martin