optimal IO scheduler choice?

optimal IO scheduler choice?

[Louis-David Mitterrand]

Hi,

after reading some interesting suggestions on kernel tuning at:

	http://hep.kbfi.ee/index.php/IT/KernelTuning

I am wondering whether 'deadline' is indeed the best IO scheduler (vs. 
anticipatory and cfq) for a soft raid5/6 partition on a server?

What is the common wisdom on the subject among linux-raid users and 
developers?

Thanks,

Re: optimal IO scheduler choice?

[Justin Piszcz]

On Thu, 13 Dec 2007, Louis-David Mitterrand wrote:

> Hi,
>
> after reading some interesting suggestions on kernel tuning at:
>
> 	http://hep.kbfi.ee/index.php/IT/KernelTuning
>
> I am wondering whether 'deadline' is indeed the best IO scheduler (vs.
> anticipatory and cfq) for a soft raid5/6 partition on a server?
>
> What is the common wisdom on the subject among linux-raid users and
> developers?
>
> Thanks,
> -
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>

I have found anticipatory to be the fastest.

http://home.comcast.net/~jpiszcz/sched/cfq_vs_as_vs_deadline_vs_noop.html

Sequential:
Output of CFQ: (horrid): 311,683 KiB/s
  Output of AS: 443,103 KiB/s

Input CFQ is a little faster.

It depends on your workload I suppose.

Justin.

Re: optimal IO scheduler choice?

[Gabor Gombas]

On Thu, Dec 13, 2007 at 06:24:15AM -0500, Justin Piszcz wrote:

> Sequential:
> Output of CFQ: (horrid): 311,683 KiB/s
>  Output of AS: 443,103 KiB/s

OTOH AS had worse latencies than CFQ AFAIR (it was quite some time ago I
last experimented). So it depends on what do you want to optimize for.

Gabor

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