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Message-ID: <20111012025918.GA16695@animx.eu.org>
Date: Tue, 11 Oct 2011 22:59:18 -0400
From: Wakko Warner <wakko@...mx.eu.org>
To: linux-kernel@...r.kernel.org
Subject: Re: Slow write performance with mpt2sas
Wakko Warner wrote:
> I've noticed that my SAS9212-4i4e is having write issues. I have a raid5 of
> 4 2tb seagate green drives and a raid5 of 3 300gb seagate 15k sas drives.
> Write performance on the green drives is fairly poor. The riad4 of 4 disks
> has a write performance of about 6-10mb/sec. My onboard sas controller
> (1068e chip IT mode) does not have this issue (I'm using raid6 on 8 of the
> same model green drives).
>
> Write performance on the 15k drives in raid 5 was 140mb/sec (4gb volume).
Sorry, this appears to be a KVM issue. I had forgotten that I was using
this under KVM. Adding cache=writeback fixed my problems (Also note, my
load before this went to >35 when writing, now it's no higher than about 9)
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