[Beowulf] Help with inconsistent network performance

Jon Forrest jlforrest at berkeley.edu
Tue Dec 18 09:21:56 PST 2007

Brendan Moloney wrote:
> Since it is a full duplex switched network, there should not be any 
> collisions happening. 

I have a similar situation with a slightly larger cluster.
At first I also thought it was a network performance
problem. But then I ran the iftop program to watch
the network in realtime and I saw that I wasn't
even close to sending enough data to tax the switch.

I still don't know the cause of the problem but
I'm pretty sure it's not cause by excessive
network traffic. I suggest you try iftop to
see what your program is really doing.

Jon Forrest
Unix Computing Support
College of Chemistry
173 Tan Hall
University of California Berkeley
Berkeley, CA
jlforrest at berkeley.edu

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