[Beowulf] Q: IB message rate & large core counts (per node) ?

Mark Hahn hahn at mcmaster.ca
Thu Feb 25 16:53:59 EST 2010


> BTW, is Cray SeaStar2+ better than IB - for nodes w/many cores ?

BW seems like a SeaStar2+ advantage, though I haven't seen any 
discussion of latency or message rate.

> And I didn't see latencies comparison for SeaStar vs IB.

my guess is that for short routes, seastar is competitive,
but can fall behind on large machines (long routes).

regardless of how tight the seastar per-hop latency is,
IB has 2.5x the per-hop fanout (2or 3 outgoing 9.6 GB links 
versus 18 outgoing 4 GB/s links).  higher radix means an 
advantage that increases with size.
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