[Beowulf] Building new cluster - estimate

[Mark Hahn]

> Space is not tight. Computer room is quite spacious but air conditioning is
> rudimental, no windows or water lines to dump the heat. It looks like a big

if space is not a big deal, why are you even thinking about rack-mount?

>> I'd recommend looking at the Intel Twin motherboard systems for this

nothing special about Intel twins afaik - AMD twins are comparable.
but it seems even sillier to go with twin systems since you say space 
is not tight, and you'd be just creating a hotter hot-spot to cool.
(ultimately, of course, 40 nodes dissipate about the same amount 
regardless of formfactor, and you need to find out whether your room
can extract around 40*400W, about 5 tons of cooling.  and supply 
that 16 kw, of course.  I haven't measured many dual-quads yet - 
the dissipation might be closer to 300W.)

>> the very maximum. The Intel twins help here again, as they have a high
>> efficiency PSU and the losses are shared between two systems. I'm not

afaik, their efficiency is maybe 10% better than more routine hardware.
doesn't really change the big picture.  and high-eff PSU's are available
in pretty much any form-factor.  choosing lower-power processors (and perhaps
avoiding fbdimms) will probably save more power than perseverating too much
on the PSU...