I have a small two-node cluster with AMD64 Opteron processors. It was
running Centos 4 and NFS performance was good while not hindering
performance. I replaced Centos with SLES 10 about 2 weeks ago and just now
got around to really hitting it hard submitting jobs. Processes that
normally took about 15 seconds such as normal IO (each processor writes its
own data file) now require 10-15 minutes. When I observed the IO status, I
the magnitude of this difference is not just a matter of tuning.
for instance, NFS exports have changed over the past few years
in whether they require the 'async' flag. that's something that can
easily cause big differences in performance. do you have a reasonable
number of nfsd's running? if UDP, are you sure you're not seeing some
problem with fragmented packets?
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