[Beowulf] specific motherboard???

Mark Hahn hahn at mcmaster.ca
Fri Dec 7 20:10:41 EST 2007


> Keep in mind that the Petsc faq mentions:
> A fast, low-latency interconnect; any ethernet, even 10 gigE cannot provide
> the needed performance.

which seems foolish on the face of it, since 10G can be fairly low latency.
for instance, Myrinet quotes 2.3 us for mx-over-myrinet on their 10G nic,
and 2.63 for mx-over-ethernet (same nic and host, fujitsu eth switch).
that's not the lowest latency interconnect, but it's a far cry from 
50 us Gb latency...

> I wouldn't assume that your workload will scale with gigE to 16 nodes.

I haven't scrutinized petsc docs, but I would expect the answer to 
depend on what you're doing and also how big a chunk you can put onto 
a single node.  standard volume/surface argument.  from 10,000 feet,
it _looks_ like petsc could be used in a pretty high-work-per-communication
manner.

> tested DDR3, but all the tests I've seen show minimal performance improvements
> at substantial price increases.

my understanding is that ddr3-ddr2 changes are largely system-level
engineering (lower voltage/power, some changes in signal handling to
improve snr and scalability.)
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