NFS load characterization studies, anyone?

[Jeffrey Mogul]

In article <23272 at mimsy.umd.edu> steve at umiacs.umd.edu (Steve D. Miller) writes:
>[ I posted this to Sun-Spots and Sun-Nets, and it occurred to me that I should
>send something out here, too.  Here goes... ]

[I'm going to try to move this discussion to comp.protocols.nfs]

>   It occurs to me that hacking the kernel to record NFS requests and
>timestamps is a reasonable way to get a handle on the request arrival
>characterization problem, and is probably a reasonable way to get a handle
>on the "which files are referenced most" problem.  That seems like an easy
>hack, so I might whip that out and see what happens.

An alternative approach would be to use a network monitoring system
(i.e., a machine with its Ethernet in promiscuous mode) to collect
all the NFS packets that go by on the net (or perhaps just all that
go to and from a given server).  Timestamps attached to the packets
by the monitor should be almost as accurate as those provided by the
server, and could also be used to order operations involving several
servers.

The advantages of using a "passive" monitor like this are that you
can monitor any server, even those for which you don't have kernel
sources, and there is no chance that the tracing will affect the
timing of the operations themselves.  The disadvantage is that it
isn't easy to guarantee that the monitor sees every packet on a busy
net.  However, I think I have the technology to do that and I might
be able to share it with someone who was seriously interested in
research in this area.

-Jeff