networking options

[Philippe Blaise - GRENOBLE]

Patrick Geoffray wrote:

> On Tue, 2002-09-24 at 17:22, Peter Kjellström wrote:
> > On Tue, 24 Sep 2002, Richard Walsh wrote:
> >
> > >
> > > All,
> > >
> > > Whoops ... down is not alway bad ... in my prior note
> > > I meant gets worse (grows larger quickly).
> >
> > Message read loud and clear :-) ...but I do disagree. SCI latency is not
> > as dependent on the size of the cluster as one might think considering
> > it's ring topology. Here are a few numbers (all application level,
> > mpi_send/recv):
>
> I agree, the latency is not at first sight affected by the rings
> topology. It has however an effect on latency when the load increases,
> when bandwidth starts to quick in.
> If you take you car to cross Los Angeles to go to LAX airport, you can
> do that in 20 minutes at 4am. At rush hour, when everybody is roughly
> trying to do the same thing, it's about 3 hours. When you share links,
> you are exposed to such load effect.
>
> The first post was talking about 1000 nodes, that's a lot of cars.
>
> > Thus, running a 512 node SCI 3d torus (8x8x8 ring dimension) would give
>
> Much more important for this cluster size (1000 nodes) is the physical
> cabling and reliability of the whole thing. You cannot use any
> interconnect today to build 512 nodes, and pardon me but you will have
> to be nuts to do it with a Torus.
>

-> You seem to forget the Cray T3E experience. SCI network solution is
very closed, isn't it ?

  Philippe.

>
> My 2 things.
>
> Patrick
> --
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> |   Patrick Geoffray, Ph.D.      patrick at myri.com
> |   Myricom, Inc.               http://www.myri.com
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