On Jul 24, 2009, at 10:37 AM, Milo Polte wrote:
On Jul 24, 2009, at 10:49 AM, Sam Lang wrote:
dd'ing from /dev/zero to /dev/null on the PVFS2 node: 1.5 GB/s
dd'ing from /dev/zero to raid locally without PVFS2: 262 MB/s
dd'ing from /dev/zero to PVFS2 on the same node or on the same
switch (doesn't seem to matter): 54 MB/s.
pvfs2fuse or kmod?
Sorry about not being clear: pvfs2fuse.
I suspect a networking issue but what's odd to me is that read
speeds are much closer to the local performance than write speeds.
Your suggestion of reading from a null-aio trove and writing to /dev/
null got more than 200 MB/s through pvfs2. Both Syncs are set to
'no' in the configuration file, so I don't expect a metadata
bottleneck. But when running IOZone, rewrite is also faster than
write. Could there be some bottleneck in the metadata updates and
growing of files?
You might be on to something there. In 2.8.1 there's a bug that
forces a sync of metadata (the size of the bstream) even when you
don't request it, and it happens even when you use null-aio. You
could try the following patch to see if that's the actual cause of
slowness for you. This is actually Phil's suggestion, so if it works
he deserves the credit there.
http://www.pvfs.org/fisheye/rdiff/PVFS?csid=MAIN:slang:20090421161045&u&N
I'm a little skeptical of the fuse interface, just because we haven't
done much testing with it. I would be curious what performance you
get with pvfs2-cp from /dev/zero. Maybe you've already done that and
I just missed it in the email thread.
-sam
Thanks.
~Milo
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