Roger, I would suspect the Lustre client side caching influencing your write performance. 10GB is not adequate, try atleast 4x of the RAM size for file-sizes. Try doing the same tests with O_DIRECT flag as it'd truly measure your disk I/O performance bypassing FS + buffer cache.
HTH, -Kums On Fri, 2008-05-30 at 16:25 -0400, Roger Spellman wrote: > I am seeing the following odd behavior. I have several OSSes, each > with a 7T RAID 5. > > > > If I use a single client to create a single 1T file which is striped > to a single OST, the performance starts off at about 400 MB/s (which > is typical for my HW), then gradually decreases, until it reaches 250 > MB/s. I’ve seen this with both IOZone and dd. > > > As an experiment, I wrote a script that creates two hundred 10G files, > without removing them. Again, the performance starts off at 400 MB/s. > But, the performance stays nearly the same throughout the test. > > > > The only difference between these tests is that in the second case, > there are lots of opens & closes, and in the first case, just a single > open and close. > > > > Can anyone explain what is happening here, and how to possible fix it? > > > > Thanks. > > > > Roger Spellman > > Sr. Staff Engineer > > Terascala, Inc. > > > > > _______________________________________________ > Lustre-discuss mailing list > [email protected] > http://lists.lustre.org/mailman/listinfo/lustre-discuss _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
