mogul@decwrl.dec.com (Jeffrey Mogul) (03/29/90)
In article <23272@mimsy.umd.edu> steve@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