[Beowulf] torus versus (fat) tree topologies

[Michael T. Prinkey]

We have in the past implemented a 2D torus network along with a switched
network.  So the 2D network handles the nearest neighbor communication and
the switch handled everything else.  For later clusters, we dropped to a
1D "torus" as most of the traffic was only travelling along one dimension.  
Most of the clusters we have built since have used this approach with good
success.  As we have moved to 1U chassis, it has been a challenge to get
three gigabit ethernet ports to even do a 1D torus plus a switch (or FNN
or much of anything else).  So in our latest cluster, we have dropped the
torus completely and, instead, added a second gigabit network using
"cheap" gigabit switches to handle I/O, logins, etc. and allow the
"expensive" gigabit network to handle the parallel traffic.

I determined early on that a torus with ethernet (fast ethernet at the 
time) was pretty much out of the question due to hugh accumulation of 
latencies as you span the torus.  Since gigabit latencies are about the 
same as fast ethernet, this situation remains the same.

Mike Prinkey
Aeolus Research, Inc.

On Wed, 10 Nov 2004, Renato S. Silva wrote:

> Hi Folks
> 
> Does anyone implement a torus topology in a cluster ?
> 
> Thanks
> Renato
> 
> 
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