On Tue, May 27, 2008 at 05:27:32PM +0200, belcampo wrote: > I've found a another workaround which works remarkebly well. > On a pvfs2-client which also is meta and io/server I mount > pvfs2-filesystem on /pvfs2 which I then export by nfs3 and localy mount > at /pvfs2nfs. rsize and wsize left out, see strace output. I accidently > discovered this by doing a simple mount -t nfs .. .. which was really > fast. When I modified fstab with .... rsize=8192,wsize=8192 which I > normally do for nfs3, performance was much less, same ffmpeg commands > resulted in a drop from fps=3129 to fps=1079, and fps=2329 to fps=610 > > mplayer /pvfs2nfs/somefile.mpg works terrific > > How bad/stupid is this workaround ?
Hi Henk This is a perfectly valid workaround. It's one we recommend for workload like yours: mplayer is a serial, read-only application, so there's no worry about NFS caching causing unexpected results for another process. As you've seen, the bigger the rsize/wsize, the better. We expect this as well. > ffmpeg -i /pvfs2nfs/some.mpg .. local/nonpvfs2/filesystem fps=3129 > ffmpeg -i /pvfs2nfs/some.mpg .. /pvfs2/filesystem fps=396 > ffmpeg -i /pvfs2nfs/some.mpg .. /pvfs2nfs/somenew.mpg fps=2329 > ffmpeg -i local/nonpvfs2/filesystem .. /pvfs2nfs/filesystem fps=1911 > > 1st is read from pvfs2 through nfs and write directly to local xfs > 2nd is read from pvfs2 through nfs and write directly to pvfs2 > 3rd is read from pvfs2 through nfs and write through nfs to pvfs2 > 4th is read from local xfs and write to pvfs2 through nfs > > 1st strace IO value for read 32768 and write 2048 > 2nd strace IO value for read 2048 and write 2048 > 3rd strace IO value for read 32768 and write 2048 > 4th strace IO value for read 32768 and write 2048 This is where NFS caching is really helping PVFS: those 2k writes are really bad for a parallel file system, but with NFS caching the writes are batched up into 32k sized operations. Much nicer. ==rob -- Rob Latham Mathematics and Computer Science Division A215 0178 EA2D B059 8CDF Argonne National Lab, IL USA B29D F333 664A 4280 315B _______________________________________________ Pvfs2-users mailing list [email protected] http://www.beowulf-underground.org/mailman/listinfo/pvfs2-users
