Re: Strange delete performance using XFS

[Thomas Kaehn <tk@westend.com>]

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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