cooling systems

Mark Hahn hahn at
Fri Apr 11 17:20:05 EDT 2003

as usual, Robert (et al) gave a comprehensive answer.
I'd like to just emphasize one thing: expect trouble if you
use chilled-water cooling that's designed/managed for offices.
ours works fairly well during the summer (16 tons of chillers and
35 KW dissipated, which should work out to 10/16 utilization.)

but facilities people tend not to think of chilled water as a 
critical resource, and construction people certainly do not.
you *will* have problems with the temperature of your chilled 
water (not to mention whether it's even flowing).  I was surprised
how little thermal capacity the chillers/pipes have - our room
heats up in seconds if there's any disruption.

and don't forget to run your chiller blowers on your UPS :(

I expect we'll be adding supplemental electical cooling soon ;(

consider wiring up a few ibutton thermo sensors - I have 5 now
(incoming chilled water pipe, chilled air duct, dead/ambient
and hot/return air), and log them every 30 seconds or so.
yes, I have a little script that monitors the temps, logs them 
in mysql, pages me, powers off.

clusters are getting bigger, and these problems aren't going away.
yes, one solution is to use laptop processors.  that works, but is 
simply inapropriate for some applications.  another is to try
water-cooling, which I've heard some cluster vendors are working on.
the main appeal there is to avoid flakey CPU fans, and potentially
to exchange and transport heat more effectively.  but you're still
probably dependent on a chiller somewhere.

regards, mark hahn.

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