Re: Strange delete performance using XFS

[Justin Piszcz <jpiszcz@lucidpixels.com>]

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On Wed, 4 Apr 2007, Thomas Kaehn wrote:

> Hi,
>
> I've got a strange problem on one machine using XFS. Deleting large
> directories (containing about 100000 files, 20k each) using "rm -rf"
> lasts nearly as long as creating the the files using a bash loop.
>
> The machine is running Debian Sarge with a vanilla 2.6.20.3 kernel.
> CPU: Dual Xeon(TM) CPU 3.20GHz
> RAM: 4 GB
> RAID10: 4x 320 GB disks connected to 3ware 9550SXU-8LP
> (Firmware Version = FE9X 3.08.00.004)
>
> The XFS was first created using default options and later on with
> "-d su=64k,sw=2 -l su=64k" which improved overall performance
> but not delete performance.
>
> Has anyone realized similar effects? On a different server (Dell 6850)
> the directory can be deleted within seconds. What could be the reason
> for the huge difference in delete performance?
>
> Please see below for "time" output.
>
> | # time for i in `seq 1 100000`; do dd if=/dev/zero of=$i bs=1k count=20 >/dev/null 2>&1; done
> |
> | real    6m6.814s
> | user    0m30.290s
> | sys     2m42.562s
> | # time rm -rf y
> |
> | real    5m18.034s
> | user    0m0.036s
> | sys     0m8.169s
>
> In contrast to this the result on the Dell machine looks more
> reasonable:
>
> | # time for i in `seq 1 100000`; do dd if=/dev/zero of=$i bs=1k count=20 >/dev/null 2>&1; done
> |
> | real    9m26.658s
> | user    0m24.134s
> | sys     3m3.623s
> | # time rm -rf x
> |
> | real    0m10.254s
> | user    0m0.124s
> | sys     0m10.105s
>
> Ciao,
> Thomas
>
> PS: Using JFS and ext3 it is also possible to delete the above directory
> in a couple of seconds. Only XFS seems problematic in this regard on
> this system.
> -- 
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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.