[Beowulf] torus versus (fat) tree topologies
joachim at ccrl-nece.de
Tue Nov 9 22:54:35 EST 2004
Greg Lindahl wrote:
> On Mon, Nov 08, 2004 at 11:45:12PM -0500, Chris Sideroff wrote:
>> I have had the luxury of testing an SCI 2D torus cluster and found
>>latency performance to be exceptional.
> Right. So is that a feature of the NIC, or a feature of the torus
> instead of a fat tree/CLOS/CBB network? Answer: the NIC.
Yes, a feature of the NIC, plus: the torus doesn't affect the latency
significantly. In fact, the cost of a hop in an SCI-based torus, like an
other reasonable modern torus, is only a low number of nanoseconds (I'd
have to look it up right now for an exact number which I can not do from
here; I think there's also such a number in a recent publication on
BlueGene). A hop in a router node has about the same delay (as it is has
a similar task).
Joachim Worringen - NEC C&C research lab St.Augustin
fon +49-2241-9252.20 - fax .99 - http://www.ccrl-nece.de
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