I meant use file-size that are 4x the RAM size :-). So if your RAM size is 4GB, use atleast 16GB file-sizes for the benchmarks.
On Fri, 2008-05-30 at 15:03 -0600, Lundgren, Andrew wrote: > Are you suggesting he use machines with 40G of RAM to work with 10G files? > > We have many 800-900G files... I am not sure that is a realistic number. > > -- > Andrew > > > -----Original Message----- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] On Behalf Of > > Kumaran Rajaram > > Sent: Friday, May 30, 2008 3:01 PM > > To: Roger Spellman > > Cc: [email protected] > > Subject: Re: [Lustre-discuss] Performance Drop creating big files > > > > 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 > > _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
