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Re: XFS vs Elevators (was Re: [PATCH RFC] nilfs2: continuous snapshottin

To: Dave Chinner <david@xxxxxxxxxxxxx>, Szabolcs Szakacsits <szaka@xxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, linux-fsdevel@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx
Subject: Re: XFS vs Elevators (was Re: [PATCH RFC] nilfs2: continuous snapshotting file system)
From: Martin Knoblauch <knobi@xxxxxxxxxxxx>
Date: Thu, 21 Aug 2008 04:05:21 -0700 (PDT)
Sender: xfs-bounce@xxxxxxxxxxx
----- Original Message ----

> From: Dave Chinner <david@xxxxxxxxxxxxx>
> To: Szabolcs Szakacsits <szaka@xxxxxxxxxxx>; Andrew Morton 
> <akpm@xxxxxxxxxxxxxxxxxxxx>; linux-fsdevel@xxxxxxxxxxxxxxx; 
> linux-kernel@xxxxxxxxxxxxxxx; xfs@xxxxxxxxxxx
> 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


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