[Beowulf] file IO benchmark

[Iozone]

Joachim wrote:


>I/O is a complex topic, and a single number rarely tells you enough if you want 
>to analyze what's going on. For this purpose, IOzone is very powerful. But 
>again, it does only run on a single node (although can fork processes/threads to 
>perform concurrent operations). You could start it on multiple nodes, but then 
>the I/O is not synchronized, which may or may not what you want to do.

>-- 
>Joachim Worringen - NEC C&C research lab St.Augustin
>fon +49-2241-9252.20 - fax .99 - http://www.ccrl-nece.de

    Iozone is able to run across multiple nodes. See the -+m and -t options.
    It knows how to use rsh and can also use any remote execution
    method by simply setting the environmental variable RSH to 
    whatever works for you. Example: RSH=ssh ; export RSH

    When Iozone is running across multiple nodes the I/O and 
    testing IS synchronized via a barrier mechanism.  Also, 
    straggler effects are minimized via the stonewalling technique
    inside of Iozone.  The technique goes like this:

    Master Iozone:  starts remote copies on all nodes.
    Client Iozone: startup, and reach barrier, then wait for go from master.
    Master Iozone: Sees all remote copies check-in at the barrier, and
                           sends message telling them to begin testing.

    First client to finish: Sends message to master, telling master, I'm done.
    Master: Sends message to all remaining instances of Iozone, telling
                them to stop measurement, as the parallel region has ended.
    Remaining clients report results to master, and exit.
    Master totals results and reports results to user.

Enjoy,
Don Capps
capps _at_ iozone _dot_ org



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