[Beowulf] Efficient UPS Aids Google?s Extreme PUE

David Mathog mathog at caltech.edu
Fri Apr 3 14:49:42 PDT 2009

Greg Lindahl
> On Fri, Apr 03, 2009 at 09:14:24AM -0700, David Mathog wrote:
> > 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 picture shows 2 things sticking out. One is the PS, the one on the
> other side is a battery. There are 2 long wires (red,black) that run
> from the battery to the PS.

Right you are.  For some reason from the top picture I thought that
thing was a control module holding a power switch underneath, but of
course looking at the third picture shows that it is a battery.  

The scale of that server is odd.  Judging from the vertically mounted
memory modules it is about 1U high, but since disk drives are only 4"
across (top to bottom in the first picture, assuming a 3.5" disk), that
makes the server width around 12" and the depth around 14".  

Anyway, it looks to me like that battery is around 5" x 2.6" x 2.5"
(about 32.5 cubic inches), whereas some 6V lead acids in a UPS I
repaired were 6 x 2 x 3.7 (about 44.4 cubic inches).  Two of these 6V
batteries went into a 675VA UPS, so with some vigorous hand waving, that
Google battery would be good for something like 675 * 0.5 * 32.5 /44.4
or around 250VA.  Plus or minus, assuming roughly the same energy
storage density.

> I can't guess how long a battery of that size would last, but probably
> more than a couple of minutes.

Probably somebody can estimate the power consumption of the board fairly
accurately, and between that and the battery size, we would have a
ballpark number.

In the last picture in the article, are those the batteries on the aisle
side or the power supplies?  It looks a bit like a power supply
(with a fan and some sort of sticker), but it also looks like it is way
off to one side of the rack, like the battery is in the top picture,
whereas the PS in the top picture is in the center.  Hmm, maybe it is a
battery, with that black strap across the front of the battery to hold
it in place. The picture showing the "rear side" of the unit looks like
all connectors are on that one side, and since the thing is in a
shipping container with no easy access to the far side of the rack, I
would have thought that all the node connectors would be on the aisle
side.  Perhaps "rear" here means "aisle"?


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

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