Re: Strange delete performance using XFS

Thomas Kaehn
2007-04-05T07:28:11Z

Hi Chris,

On Wed, Apr 04, 2007 at 08:45:23AM -0700, Chris Wedgwood wrote:
> On Wed, Apr 04, 2007 at 03:05:35PM +0200, Thomas Kaehn wrote:
> > 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.
>
> have you tried w/o using the hw raid?

I'am going to test with a single disk in the same machine.

> > 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?
>
> a lot of log updates; does the other server have a battery-backed
> write-cache like many cards to these days?

The Dell system has got a battery-backed write-cache. The 3ware system
has no battery unit. However it's supposed to provide write cache, too.
At least I've enabled it in the RAID's configuration. The controller
has got more than 100MB memory.

> > | # 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
>
> that's about the same as my quick single-spindle cheap-desktop test
> here
>
> > | # time rm -rf y
> > |
> > | real 5m18.034s
> > | user 0m0.036s
> > | sys 0m8.169s
>
> v2 logs? what logbufs & logbsize is used?
>
> testing with my cheap crappy desktop workstation thing with a
> single disk I get "1m25.004s" for the delete

Your delete time sounds more sensible to me. The file system was
created first with default options - later on I tried to match
the RAID's stripe size, increased the log size and mounted
with logbufs=8:

log stripe unit specified, using v2 logs
meta-data=/dev/sda1 isize=256 agcount=8, agsize=125008 blks
= sectsz=512
data = bsize=4096 blocks=1000032, imaxpct=25
= sunit=16 swidth=32 blks, unwritten=1
naming =version 2 bsize=4096
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=512 sunit=16 blks
realtime =none extsz=65536 blocks=0, rtextents=0

Ciao,
Thomas
--
Thomas Kähn WESTEND GmbH | Internet-Business-Provider
Technik CISCO Systems Partner - Authorized Reseller
Im Süsterfeld 6 Tel 0241/701333-18
tk@westend.com D-52072 Aachen Fax 0241/911879
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Die Gesellschaft ist eingetragen im Handelsregister Aachen unter HRB 7608
Geschäftsführer: Thomas Neugebauer, Thomas Heller, Michael Kolb