[Beowulf] Power draw of cluster nodes under heavy load

Mark Hahn hahn at mcmaster.ca
Mon Jul 28 15:09:59 PDT 2014

> Some involved in the discussion have stated only 5 - 10 kW per full rack,

always nice when people clearly declare themselves to be useless.

> which is too small. Since I don't know exactly what systems I'm going to get 
> from my RFP, I can't do exact calculations based on specific models. I could

RFP is a fatally flawed process, though vendors seem to like it,
and it's formal enough to make paper-pushers think it's sensible.

OTOH, you can be pretty specific in your RFP: for instance, you
should be able to specify max total power, max power-per-node, etc.
don't forget PSU efficiency: a system drawing 300W from a 94%
"eighty-plus-platinum" is 319 at the plug, but a crappy old 70%
PSU will be nearly 430W!  higher-end PSUs also have flatter
efficiency curves in the middle, though unfortunately, they usually
peak at 50% (and from examples here:
it looks like certification only requires testing at 10/20/50/100% load)

regards, mark hahn.

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