32-port gigabit switch

[Rogerio Luiz Iope]

Hi all,

I'm in the early stages of building a 32-node beowulf
cluster, and I'm looking for a really _low-cost_
32-port (or more) gigabit switch for the LAN interconnection.
I was wondering if I could use e.g. Foundry EdgeIron
model 24G. But in that case it would be necessary to use
two of them because, as the name implies, it's a 24-port model.
I suppose, however, that it's not a good idea to simply
link-aggregate them, because in that case it would not be an
interconnect topology with full bisection bandwidth.
I was told about using the 'flat neighborhood network'
topology as a cheap alternative, using three 24G switches and two
NICs on each node, but I have no idea if it's a good solution or not,
and I think it would be hard to configure and to scale.
It's important to mention that the interconnect structure I'm looking for
should be easy to scale, up to maybe 128 compute nodes or so,
maintaining full bisection bandwidth. Oh, yeah, we have a very limited
budget, so at the present moment, Myrinet is out of question.

I apologise if these are only simple questions, but I'm a newbie in the
field, and I really need some help. I'd be glad to listen to the experts.

Thanks in advance,

Rogerio L. Iope
University of Sao Paulo - Brazil
phone: 55-11-3091-6461