Cisco switches for lam mpi

Felix Rauch rauch at
Mon Aug 4 08:02:50 EDT 2003

On Tue, 29 Jul 2003, Jack Douglas wrote:
> We have just installed a 32 Node Dual Xeon Cluster, with a Cisco Cataslyst
> 4003 Chassis with 48 1000Base-t ports.
> We are running LAM MPI over gigabit, but we seem to be experiencing
> bottlenecks within the switch
> Typically, using the cisco, we only see CPU utilisation of around 30-40%

I'm not a Cisco expert, but...

We once got a Cisco switch from our networking people that we had to
return immediately because it delivered such a bad performance. It was
a Catalyst 2900XL with 24 Fast Ethernet ports, but it could only
handle 12 ports at full speed. Above that, the performance brake down

For some benchmark results see, e.g.:

As a comparison, the quite nice results of a CentreCom 742i:

Disclaimer: Maybe the Cisco you mentioned is better, or Ciscos improved
anyway since spring 2001 when I did the above tests. Besides, the
situation for Gigabit Ethernet could be different.

As we described on our workshop paper at CAC03 you can not trust the
data sheets of switches anyway:

Conclusion: If you need a very high performing switch, you have to
evaluate/benchmark it yourself.

- Felix

Felix Rauch                      | Email: rauch at
Institute for Computer Systems   | Homepage:
ETH Zentrum / RZ H18             | Phone: +41 1 632 7489
CH - 8092 Zuerich / Switzerland  | Fax:   +41 1 632 1307

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