[Lustre-discuss] Fwd: max_sectors_kb change doesn't help

[Andreas Dilger]

On Sep 27, 2007  10:40 +0200, Erich Focht wrote:
> On Thursday 27 September 2007 01:20, Andreas Dilger wrote:
> > On Sep 26, 2007  17:50 +0200, Erich Focht wrote:
> > > in 512K pieces. Following the Lustre manual I changed
> > > /sys/block/DEVICE/queue/max_sectors_kb to 1024 but the I/O sizes in Lustre
> > > didn't change.
> > 
> > Did you try remounting the OSTs after changing the setting?
> 
> Yes, actually when I changed the settings the lustre modules were not loaded,
> yet. Where is the detection of the maximally allowed I/O size done in Lustre?

In fact there isn't any such detection in Lustre - it will push pages into
an IO until the block layer tells it to stop.

Please check /proc/fs/lustre/obdfilter/*/brw_stats to see if the IO requests
coming from the client are 1MB in size (256 pages), and if yes then the issue
would likely be in the block layer.

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.