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Re: Strange delete performance using XFS

To: Thomas Kaehn <tk@xxxxxxxxxxx>
Subject: Re: Strange delete performance using XFS
From: Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx>
Date: Wed, 4 Apr 2007 14:36:37 -0400 (EDT)
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20070404134724.GF18320@xxxxxxxxxxxxxxxxxx>
References: <20070404130535.GE18320@xxxxxxxxxxxxxxxxxx> <Pine.LNX.4.64.0704040928110.7309@xxxxxxxxxxxxxxxx> <20070404134724.GF18320@xxxxxxxxxxxxxxxxxx>
Sender: xfs-bounce@xxxxxxxxxxx

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.

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For the ext3, try time bash -c 'rm -rf test; sync'
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