linux-kernel - Re: RAID extremely slow

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Date:	Sat, 28 Jul 2012 01:34:38 -0700
From:	Kevin Ross <kevin@...ilyross.net>
To:	Grant Coady <gcoady.lk@...il.com>
CC:	Bill Davidsen <davidsen@....com>,
	Linux RAID <linux-raid@...r.kernel.org>,
	Linux Kernel mailing List <linux-kernel@...r.kernel.org>
Subject: Re: RAID extremely slow

On 07/27/2012 09:45 PM, Grant Coady wrote:
> On Fri, 27 Jul 2012 14:45:18 -0700, you wrote:
>
>> On 07/27/2012 12:08 PM, Bill Davidsen wrote:
>>> Have you set the io scheduler to deadline on all members of the array?
>>> That's kind of "job one" on older kernels.
>>>
>> I have not, thanks for the tip, I'll look into that now.
> Plus I disable the on-drive queuing (NCQ) during startup, right now
> I don't have benchmarks to show the difference.  This on a six by 1TB
> drive RAID6 array I built over a year ago on Slackware64-13.37:
>
> # cat /etc/rc.d/rc.local
> ...
> # turn off NCQ on the RAID drives by adjusting queue depth to 1
> n=1
> echo "rc.local: Disable RAID drives' NCQ"
> for d in a b c d e f
> do
>          echo "  set NCQ depth to $n on sd${d}"
>          echo $n>  /sys/block/sd${d}/device/queue_depth
> done
> ...
>
> Maybe you could try that?  See if it makes a difference.  My drives
> are Seagate.
>
> Grant.
>

Does disabling NCQ improve performance?

The suggestion to use kernel 3.4.6 has been working quite well so far, 
hopefully that fixes the problem.  I'll know for sure in a few more days...

Thanks!
-- Kevin

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