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

Dave Chinner
2012-06-15T12:30:37Z

On Fri, Jun 15, 2012 at 01:25:26PM +0200, Bernd Schubert wrote:
> 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.

Sounds like a case of the IO scheduler queue and/or CTQ being too
deep.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com