[Beowulf] Efficient UPS Aids Google?s Extreme PUE

[David Mathog]

Nifty Tom Mitchell <niftyompi at niftyegg.com> wrote
> 
> I suspect that the UPS component is very short.  i.e. finish the current
> search, notify the distributed google world that the 'node' is going
> off line and then go off line.  I doubt that the specifications for the
> UPS are hours or days the way a national weather center or hospital data
> center or other critical resource is specified.   If someone post a pool
> for the UPS time factor put me down for 15min.

Pretty much what I was thinking too.

In the picture on the OP's link the external PS does not look any bigger
than a standard unit, which leaves very little room in it for the UPS
battery.  The primary purpose of the UPS is most likely just to give
them a few minutes leeway to turn on the data center's generators when
the main power fails.  Even a couple of minutes UPS coverage is plenty
to allow them to save significant money on the backup
generators/failover circuitry.  Also, a smaller battery wouldn't have
the weight penalties of the sorts of sealed lead acid batteries usually
found in a UPS.  And there could be some other advantages, for instance,
they could throw the main breaker on a rack (assuming it is wired that
way), move the common plug from one circuit to another, and then close
the breaker again, all without losing service.  Big central UPS units
don't provide that sort of flexibility.

Regards,

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