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Re: Filesystem writes on RAID5 too slow

To: Martin Boutin <martboutin@xxxxxxxxx>
Subject: Re: Filesystem writes on RAID5 too slow
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Fri, 22 Nov 2013 01:23:25 -0800
Cc: Dave Chinner <david@xxxxxxxxxxxxx>, Eric Sandeen <sandeen@xxxxxxxxxx>, xfs-oss <xfs@xxxxxxxxxxx>
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On Thu, Nov 21, 2013 at 11:35:14AM -0500, Martin Boutin wrote:
> Sorry for the spam but I just noticed that the XFS stripe unit does not
> match the strip unit of the underlying RAID device. I tried to do a
> mkfs.xfs with a stripe of 512KiB but mkfs.xfs complains that the
> maximum stripe width is 256KiB.

Yeah.  Btw, I've generally seen best results using 32k stripes, but that
should only matter for log intensive loads and not simple writes.
Similarly your 32mb log seems awfully small, but not really relevant for
this workload.

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