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Re: Strange delete performance using XFS

To: Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx>
Subject: Re: Strange delete performance using XFS
From: Thomas Kaehn <tk@xxxxxxxxxxx>
Date: Thu, 5 Apr 2007 10:17:51 +0200
Cc: xfs@xxxxxxxxxxx
In-reply-to: <Pine.LNX.4.64.0704041012500.7309@xxxxxxxxxxxxxxxx>
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Hi Justin,

On Wed, Apr 04, 2007 at 10:13:36AM -0400, Justin Piszcz wrote:
> I used the DEFAULT create options for XFS as I find it highly optimizes 
> itself (at least with SW raid) with the exception of the ROOT FS, I had 
> that optimized awhile ago and I kept it:
> 
> /dev/md2       /            xfs 
> logbufs=8,logbsize=262144,biosize=16,noatime,nodiratime,nobarrier  0  1
> 
> 
> For my regular RAID5s though I use defaults,noatime.

I've disabled barriers, too, and performance increased dramatically.

However I am not aware of the consequences of disabling write barriers.
The FAQ generally recommends using write barriers except when having
a battery-backed cache (this 3ware has not).

| # time for i in `seq 1 100000`; do dd if=/dev/zero of=$i bs=1k count=20 
>/dev/null 2>&1; done
| 
| real    3m52.182s
| user    0m30.482s
| sys     3m16.152s
| 
| # time \rm -rf y
| 
| real    0m16.327s
| user    0m0.052s
| sys     0m8.305s

So I am unsure if disabling is an option for me. I could imagine
that write barriers are not properly supported by 3ware or have
to be fine tuned at the kernel or SCSI level.

Ciao,
Thomas
-- 
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