[Beowulf] Re:UPS system for Linux cluster

David Mathog mathog at caltech.edu
Thu Apr 30 14:02:47 EDT 2009

John Bushnell <john.bushnell at icb.ucsb.edu> wrote:

> Another reason for not having UPS power for an entire cluster is 
> cooling.  In our server room, if we lose regular power, we lose our 
> large AC units as well.  So we need to be careful what we keep plugged 
> into our emergency power circuits (a relatively tiny amount of 
> equipment).  Having an entire stack of nodes churning away during a  
> power outage would kill us pretty quickly.

Excellent point.  Like most cooling on campus, the AC in my machine room
dumps heat into chilled water lines.  Eventually that heat is
transferred from the water to the atmosphere at a cooling tower several
hundred meters away in the central plant.  I don't know if central plant
has a backup generator to circulate and cool the water.  Assuming not,
even if this machine room had a UPS big enough to keep everything
running, including the fans on the AC unit, there would still be no way
to cool the room.   Even if a backup generator is present at the central
facility, I am pretty sure the powers that be would prefer the machine
rooms turn off during the power outage, so that whatever cooling
capacity remains may be used for more critical tasks. For instance,
keeping cold rooms and animal facilities at safe temperatures.


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