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

[Erich Focht]

On Tuesday 02 October 2007 07:10, Andreas Dilger wrote:
> > Could this problem come from multipath? It is "assembling" the dm-* devices
> > out of the SCSI devices, presents the SCSI devices as "slaves", but has no
> > own settings for the queue parameters in /sys/block/dm-*. I tried increasing
> > the SCSI member devices' queue max_sectors_kb before starting the multipathd,
> > but it didn't help. Uhmmm, yes, I am using multipath... forgot to mention
> > earlier.
> 
> It seems entirely possible, I haven't looked at the multipath code myself.
> It should really build the q->max_* values as the minimum of all of the
> underlying devices instead of using a default value.

Without multipath (mounting the scsi devices directly) the change of
max_sectors_kb has the expected effect: Lustre stops to fragment and I/Os
are done in 1MB chunks. I recon I was unable to find the place where
max_sectors for the multipath queues is set, will continue to look into this.

Regards,
Erich