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

[Bernd Schubert <bernd.schubert@xxxxxxxxxxxxxxxxxx>]

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