On Fri, 17 Nov 2006, jan taubert (RRes-Roth) wrote:
Second test: Using BLAST 2.2.15 formatdb command for the nr (2155MB)
database "time formatdb -i nr"
Lustre:
real 12m42.931s
user 3m29.847s
sys 9m9.381s
Attached storage:
real 4m6.323s
user 3m21.581s
sys 0m43.857s
Why is the attached storage in this case three times faster then the
Lustre filesystem? When you compare the two "time" outputs you see that
the "sys" part is much higher on Lustre than on the attached storage.
Any suggestions, what I did wrong?
You did not necessarily do anything wrong, but some workloads require
additional tuning, and in some cases local storage can be faster than
Lustre.
I don't know the program you used at all, but it sounds like it could be
performing lots of small I/Os and/or operate on many small files.
The output of "strace -fc formatdb ..." (maybe with a smaller working set)
would certainly give us hints, and the full output of "strace -fttT ..."
can be useful as well (unless this program uses mmap() for I/Os).
If the program operates on large files, then you should probably look at
striping parameters (eg. stripe over all OSTs, and try different stripe
sizes).
HTH
--
Jean-Marc Saffroy - [EMAIL PROTECTED]
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