|
Beowulf users,
The information posted to this
list concerning the proper mechanism
for running Iozone in parallel across the nodes is
incorrect. You do
NOT use dsh or any other parallel tool. It is NOT
needed. Iozone
already knows how to go parallel across nodes. See
-+m option.
If you follow this person's
suggestion you will get wrong answers,
and prove that you have never read the manual, nor
the man page,
nor even the help screen.
If you use the -+m option then
Iozone will eliminate the
straggler effect (some finish early, others finish
late) and
be able to obtain accurate throughput
results.
Below is the mis-information that was posted. ( It
is wrong, please
ignore this mis-information)
Enjoy,
Don Capps
-----------
Egan Ford egan
at sense.net
Thu Jan 5 15:54:00 PST 2006
Find a parallel shell (e.g. pdsh), then write a script to run iozone, something like: echo ready while [ ! -r /other/nfs/fs/go ] do sleep .1 done cd /nas/fs iozone option option option ... >/other/nfs/fs/iozone.$(hostname -s).out exit 0 Use pdsh or other to run the script on all nodes, e.g.: date >foo;pdsh ...;date >>foo Poor man parallel shell example: date >foo;for i in node1 node2 node3 ... do ssh $i script & done;wait;date >>foo then type: touch /other/nfs/fs/go I do not recommend summing the output of iozone when running in parallel. If you have a lot of clients they will not all start at the same time, some may block on I/O for some period of time before starting inflating the performance. It is better to do the math yourself by using the timestamps in the foo file. A better solution to all of this is to use iometer. With iometer you launch a daemon on each node, then startup a iometer GUI (on Windows). The GUI can contact all the daemons and coordinate a benchmark in parallel, isolating read from write. With iozone in parallel you may get read and write overlap. You will need to patch iometer to use a directory instead of the root of the FS or all daemons will try to read/write the same name. I have a patch somewhere to use a shell variable. Another solution would be to use an MPIIO benchmark. Normally I only use iozone for testing individual drive performance on nodes and then check for a normal distribution. I use MPIIO benchmarks and iometer for testing SAN, NAS, and Parallel file systems. |
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