Re: Strange delete performance using XFS

[Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx>]

On Wed, 4 Apr 2007, Justin Piszcz wrote:

> On Wed, 4 Apr 2007, Thomas Kaehn wrote:
>
> > Hi Justin,
> >
> > On Wed, Apr 04, 2007 at 09:29:46AM -0400, Justin Piszcz wrote:
> > > > Please see below for "time" output.
> > > >
> > > > | # time for i in `seq 1 100000`; do dd if=/dev/zero of=$i bs=1k count=20
> > > > > /dev/null 2>&1; done
> > > > |
> > > > | real    6m6.814s
> > > > | user    0m30.290s
> > > > | sys     2m42.562s
> > > > | # time rm -rf y
> > > > |
> > > > | real    5m18.034s
> > > > | user    0m0.036s
> > > > | sys     0m8.169s
> >
> > > Deletes on XFS is one area that is a little slower than other filesystems.
> > > You can increase the log size during the creation of the filesystem and
> > > also increase logbufs to 8 and that might help.
> >
> > Thanks for your suggestions.
> >
> > I also tried to increase the log size and logbufs mount option. This
> > optimizes create and delete times to the above values (with default options
> > both are around 9-10 minutes).
> >
> > The strange thing is that on a similar Dell machines using XFS, too,
> > deletes take only ten seconds which would match user and system time.
> >
> > More than five minutes for deleting 100000 files where ext3 needs
> > 3 seconds on the same machine is actually more than a little bit slower
> > - to my mind there must be something wrong. JFS needs around 18 seconds.
> >
> > However I am not sure if the problem is hardware or software related.
> > I've also tried to use the newest 3ware firmware - but this did not lead
> > to an improvement.
> >
> > Ciao,
> > Thomas
> > --
> > Thomas Kähn                   WESTEND GmbH  |  Internet-Business-Provider
> > Technik                       CISCO Systems Partner - Authorized Reseller
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>
> The benchmark:
> $ time for i in `seq 1 100000`; do dd if=/dev/zero of=$i bs=1k count=20 
> > /dev/null 2>&1; done
>
> 1. Six 400GB SATA drives using SW RAID5:
> real    6m24.411s
> user    0m43.097s
> sys     2m17.350s
>
> 2. Four Raptor 150 ADFD drives using SW RAID5:
> real    3m16.962s
> user    0m42.899s
> sys     2m15.420s
>
> 3. Two Raptor 74GB *GD drives using SW RAID1:
> real    3m19.241s
> user    0m41.731s
> sys     2m15.873s

I used the DEFAULT create options for XFS as I find it highly optimizes 
itself (at least with SW raid) with the exception of the ROOT FS, I had 
that optimized awhile ago and I kept it:

/dev/md2       /            xfs 
logbufs=8,logbsize=262144,biosize=16,noatime,nodiratime,nobarrier  0  1


For my regular RAID5s though I use defaults,noatime.

Justin.