One simple but absolutely invaluable tool to diagnose NFS performance problems is the nfsstat command. As it gives you good numbers about many parts of the NFS subsystem, it's easy to recognize imbalances in the number of commands going over the wire. It's the first tool i'm using, when i'm at a customer site to say a word or two about NFS performance or - better - the absence of it. You can recognize inadequate settings of caching mechanisms with a short look on the numbers for example. So it's nice to see, that there is an open PSARC case with 2010/120 to introduce a similar tool for the in-kernel SMB stack.

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