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

[Brian Dobbins]

Hi guys,

  I'm beginning to look into configurations for a new cluster and with the
AMD 12-core and Intel 8-core chips 'here' (or coming soonish), I'm curious
if anyone has any data on the effects of the messaging rate of the IB
cards.  With a 4-socket node having between 32 and 48 cores, lots of
computing can get done fast, possibly stressing the network.

  I know Qlogic has made a big deal about the InfiniPath adapter's extremely
good message rate in the past... is this still an important issue?  How do
the latest Mellanox adapters compare?  (Qlogic documents a ~30M messages
processsed per second rate on its QLE7342, but I didn't see a number on the
Mellanox ConnectX-2... and more to the point, do people see this effecting
them?)

  On a similar note, does a dual-port card provide an increase in on-card
processing, or 'just' another link?  (The increased bandwidth is certainly
nice, even in a flat switched network, I'm sure!)

  I'm primarily concerned with weather and climate models here - WRF, CAM,
CCSM, etc., and clearly the communication rate will depend to a large degree
on the resolutions used, but any information, even 'gut instincts' people
have are welcome.  The more info the merrier.

  Thanks very much,
  - Brian
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