Mark,
At 15:09 31.01.2008, Mark Hahn wrote:
I did not claim the opposite - I said that for small, cost-sensitive
clusters, it would be unusual to need IB's advantages (high bandwidth
and latency comparable to other non-Gb interconnects.)
in particular, I'm curious about the conventional wisdom about weather codes
and bandwidth.
k
I was curious about this: you only used one DDR port; was that because
of lack of switch ports, or because WRF uses bandwidth <= DDR?
The system is a general purpose benchmarking system; not particularly
crafted for running WRF. Based on a slightly apples-to-oranges
comparison, you will see that QLogic's SPEC MPI2007 submission
contains a WRF number (374s) which is _very_ similar to what I
reported. This is an indiction that WRF on this system / dataset is
not restricted by SDR bandwidth (also, for the record, this is a
slightly mix of compilers, Pathscale 3.0 and Intel 9.1, - but
they both do a decent job on WRF).
sure, and these are very fat nodes for which a fat interconnect is
appropriate for almost any workload that's not embarassing. but really
I wasn't suggesting that plain old Gb (bandwidth in particular) was
adequate for all possible clusters. I was questioning whether IB
was a panacea for small, cost-sensitive ones...
I do not agree that dual-socket, dual-core Woodcrest nodes these
days are "very fat". A quad-socket, quad-core is. A quad-socket,
dual-core or a dual-socket, quad-core might be considered semi-fat...
Hakon
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