>>> 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.
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