[Beowulf] /. Cooler room or cooler servers?

David Mathog mathog at mendel.bio.caltech.edu
Thu Apr 7 20:46:00 EDT 2005


> From: "Robert G. Brown" <rgb at phy.duke.edu>

> > Thats dual 32bit xeons, the dual em64t xeon systems are more like 420W.
> > 
> > Michael
> 
> Wow, that's Hot.  That's actually getting up there to the old alpha
> boxen, per CPU.  So 40 1U systems are order of 16 KW/rack?  Five tons of
> AC per rack?  $400/year/box for power and cooling (or thereabouts)?
> Oooo.

Convert 16KW to horsepower and find 16000 * .00134  => 214 hp.
The point being that car engines generate this much heat in an
even smaller space (1/3 to 1/4 of a rack volume, including the
block and not just the cylinders).  Automobile engineers resolve
this issue by dumping the heat as fast as they
possibly can.   It's interesting to compare and contrast the
way a car motor is cooled with the way a computer is cooled.

1.  Car motors are cooled by ambient input air - I've never seen
a car that prechills its cooling air.    Nor is the cooling air
blowing over the radiator particularly clean.

2.  There have been smallish air cooled motors but I can't think 
of any car motors over 200 hp that were air cooled.  Aircraft motors
that big may be aircooled but in that case there is typically
in excess of 100 kph in air flow available.  So expect either
wind tunnel speeds for computer cooling air or water cooling.

3.  There comes a point where there is so much heat produced it simply
doesn't make sense to try to cool the outlet air and run it back around
to the input.  Instead the hot air is blown directly out of the
building, with care taken to keep it away from the intakes. In which
case either the computer needs to be able to breathe (what would
now be considered) very dirty air or the intake system needs
to filter a lot of particulates out very quickly. For sites
where the weather get really hot it might still be necessary
to cool the ambient intake air on some days, since 100F air is really
too hot to cool a CPU or disk drive effectively.

Perhaps we should be looking forward to chimneys and/or cooling towers
in future computer room designs?

Regards,

David Mathog
mathog at caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech
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