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<p>Hi All,<br>
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<p>Thanks to Doug and Kevin for the replies. In answer to Kevin's question about our choice of clustering solution for NFS: the choice was made hoping to maintain some simplicity by not using more than one HA solution at a time. However, it seems that this
choice might have introduced more wrinkles than it's ironed out.<br>
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<p>An update on our situation: we have actually uncovered another clue since my last posting. One thing that this now known to be correlated *very* closely with instability in the NFS layer is running `mmcrsnapshot`. We had noticed that flapping happened
like clockwork at midnight every night. This happens to be the same time at which our crontab was running the `mmcrsnapshot` so, as an experiment, we moved the snapshot to happen at 1a.</p>
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<p>After this change, the late-night flapping has moved to 1a and now happens reliably every night at that time. I saw a post on this list from 2013 stating that `mmcrsnapshot` was known to hang up the filesystem with race conditions that result in deadlocks
and am wondering if that is still a problem with the `mmcrsnapthost` command. Running the snapshots had not been an obvious problem before, but seems to have become one since we deployed ~300 additional GPFS clients in a remote cluster configuration about
a week ago.</p>
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<p>Can anybody comment on the safety of running `mmcrsnapshot` with a ~300 node remote cluster accessing the filesystem?</p>
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<p>Also, I would comment that this is not the only condition under which we see instability in the NFS layer. We continue to see intermittent instability through the day. The creation of a snapshot is simply the one well-correlated condition that we've discovered
so far.</p>
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<p>Thanks so much to everyone for your help :)<br>
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<p>Stewart<br>
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