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From artnaseef <...@artnaseef.com>
Subject Re: question for users of NFS master/slave setups
Date Tue, 01 Mar 2016 19:58:04 GMT
So 15 seconds sounds really low, although I'm not sure of all the various
timeout settings in NFS.

Specifically here, the timeout of concern is the release of a lock held by a
client.  The higher the timeout, the less likelihood of two clients
obtaining the same lock, but the slower failover becomes because of the
added time to detect that the lock-holder is out-of-service.  On the other
hand, the lower the timeout, the greater the chances of two clients getting
the same lock, but the faster failover becomes.

I tend toward wanting reliability first, and fast recovery time second. 
Although that really depends on the use-case.  However, for use-cases that
require very fast recovery, I would look to non-persistent messaging,
eliminating the issue of storage locking, but then requiring an alternate
approach to handling potential message loss.

The timeout here is one that must be handled by the server - whether the
server allows different clients to request different timeout values, I don't
know - but it's the NFS server that must apply it, because it needs to take
effect when the client drops off the network unexpectedly.

Hope this helps.

BTW - if the two-active-broker scenario happens very commonly and the
network appears to be performing well, then I would look to the possibility
of the lock file getting removed somehow during startup.



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