Re: Strange delete performance using XFS

Thomas Kaehn
2007-04-04T14:35:52Z

Hi Justin,

On Wed, Apr 04, 2007 at 10:24:42AM -0400, Justin Piszcz wrote:
> >On Wed, Apr 04, 2007 at 10:12:48AM -0400, Justin Piszcz wrote:
> >>On Wed, 4 Apr 2007, Justin Piszcz wrote:
> >>>On Wed, 4 Apr 2007, Thomas Kaehn wrote:
> >>>$ time for i in `seq 1 100000`; do dd if=/dev/zero of=$i bs=1k count=20
> >>>>/dev/null 2>&1; done
> >>>
> My guess is mkfs.xfs cannot optimzie for your array like it can with a SW
> RAID device because it cannot see what is undereath it. Have you tried
> making a SW RAID? I also use optimized parameters for my SW RAID1/5 as
> well FYI.

I guess this might be the problem. I've already tried to alter
the stripe unit to match the RAID stripe size: "-d su=64k,sw=2 -l su=64k".

Maybe the 3ware controller can't deal with the kind of read and write
patterns needed by XFS. But in this case other people should have
realized similar problems.

On a different system with a 3ware 9500S-4LP using 4 disks as RAID5
setup I get a better (but not really good) result for delete
performance (I've taken only 50000 files in this case as the system's
CPU is much slower):

| # time for i in `seq 1 50000`; do dd if=/dev/zero of=$i
| bs=1k count=20 >/dev/null 2>&1; done
|
| real 18m21.643s
| user 0m55.727s
| sys 3m12.140s
| backup:/srv/x# cd ..
| backup:/srv# rm -rf x
|
| # time rm -rf x
|
| real 5m7.845s
| user 0m0.160s
| sys 0m11.369s

Ciao,
Thomas
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