>>> Not sure what those do, but lsof should show what files are open, and >>> 'strace -p process_id' would show the system calls issued by a >>> process. >> >> Thanks, that might be usefull. I'ill just have to find a way to strace >> multiple process at once and find the usefull info among that load of >> data... > > Note that if what is really happening is that different processes are > frequently accessing the same disk in different locations (a fairly > likely scenario) the time will be mostly taken by the head seeks in > between and may be hard to pin down. I found the -f option to strace is able to attach to the forked child of a parent process, so I will be using that in my debuging in conjunction witgh -e to filter out only the calls I want to see... But indeed, that might be hard to find. In one case, I want to see what files are opened / accessed on a gfs2 volume over a fiber channel link to a raid-1 array, and the controler is supposed to intelligent enough to distribute the read access across the 2 disks. And in the other case, it's an ssd, so seek time should be 0.