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Re: XFS hangs and freezes with LSI 9265-8i controller on high i/o

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: XFS hangs and freezes with LSI 9265-8i controller on high i/o
From: Bernd Schubert <bernd.schubert@xxxxxxxxxxxxxxxxxx>
Date: Fri, 15 Jun 2012 13:25:26 +0200
Cc: Matthew Whittaker-Williams <matthew@xxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <20120615001602.GF7339@dastard>
Newsgroups: gmane.comp.file-systems.xfs.general
References: <4FD66513.2000108@xxxxxxxxx> <20120612011812.GK22848@dastard> <4FD766A7.9030908@xxxxxxxxx> <20120613011950.GN22848@dastard> <4FD8552C.4090208@xxxxxxxxx> <20120614000411.GY22848@dastard> <4FD9F5B3.3040901@xxxxxxxxx> <20120615001602.GF7339@dastard>
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On 06/15/2012 02:16 AM, Dave Chinner wrote:
Oh, I just noticed you are might be using CFQ (it's the default in
dmesg). Don't - CFQ is highly unsuited for hardware RAID - it's
hueristically tuned to work well on sngle SATA drives. Use deadline,
or preferably for hardware RAID, noop.

I'm not sure if noop is really a good recommendation even with hw raid, especially if the the request queue size is high. This week I did some benchmarks with a high rq write size (triggered with sync_file_range(..., SYNC_FILE_RANGE_WRITE) ) and with noop concuring reads then almost entirely got stalled. With deadline read/write balance was much better, although writes still had been preferred (with sync_file_range() and without). I always thought deadline prefers reads and I hope I find some time later on to investigate further what was going on.
Test had been on a netapp E5400 hw raid, so rather high end hw raid.


Cheers,
Bernd


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