> Hi Nicolas, > > While this doesn't exactly answer your question, I was wondering what > scheduler you were using on your GFS2 (Note: I have not used this file > system before) block. You can find this by issuing 'cat /sys/block/<insert > block device>/queue/scheduler' ? > > By default the system uses cfq, which will show up as [cfq] when catting > the scheduler as I showed above. This is not the most optimal scheduler > for a webserver. In most cases you'd be better off with deadline or noop. > Not being familiar with GFS2 myself, I did skim this article, which makes > me think noop would be the better choice: > > http://www.redhat.com/archives/linux-cluster/2010-June/msg00027.html > > This could be why you are seeing the processes waiting on I/O. > In my case, /sys/block/dm-9/queue/scheduler show : none and /sys/block/sdb/queue/scheduler shows "noop anticipatory deadline [cfq]". Since this is a production cluster, I do not want to make changes to it just now. I will ask advice from RHEL support for setting this. But that seems logical. In the meen time, I'd still like to find a tool to know what files are requeted to the filesystem and what ones are being waited for... Thanks