Re: Strange delete performance using XFS

Thomas Kaehn
2007-04-05T08:17:57Z

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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