[Beowulf] Re:running hot?

Bill Broadley bill at cse.ucdavis.edu
Thu Mar 19 15:39:26 EDT 2009


David Mathog wrote:
> Mark Hahn <hahn at mcmaster.ca> wrote:
> 
>> are you running your machinerooms warm to save power on cooling?
> 
> How much would that really save?  Is there a study somewhere
> demonstrating substantial power savings?

There's a data center going in the bay area and with a few concession from
vendors they were able to rise the standard temperature enough so they will be
able to run their cooling approximately 100 hours a year.

> Whatever the steady state temperature in the room the AC still has to
> pump out heat at the same rate it is generated. 

Exactly right.

> Raising the room
> temperature could affect heat exchange slightly because of a
> steeper/shallower T gradient across the walls/floor/ceiling.  For
> instance, increasing RT would let a little more power drain out through
> the walls instead of the AC, assuming it is cooler outside than inside.  
> 
> Does a PC doing the same work uses more or less power at 70 or 80 degrees?

Don't forget to factor in the ambient temp.  Say it's 70F, it's much easier to
extract useful cooling from 70F air if your internal temperature is 100F
instead of 80F.

> Off the top of my head I wouldn't expect a huge change in either number
> for a 10 degree RT change.  Maybe it makes a big difference if the
> machine room is very poorly insulated.

Sounds like you are assuming a mostly closed system, it's not.

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