[Beowulf] Efficient UPS Aids Google’s Extreme PUE

Eugen Leitl eugen at leitl.org
Thu Apr 2 02:02:43 PDT 2009


Efficient UPS Aids Google’s Extreme PUE

April 1st, 2009 : Rich Miller

Google continues to improve its energy efficiency, and is telling the
industry how it’s doing it. After years of secrecy surrounding its data
center operations, Google is disclosing many of its innovations today at the
first  Google Data Center Efficiency Summit in Mountain View, Calif.

In a morning presentation, Google engineers addressed its Power Usage
Effectiveness (PUE) ratings, which have generated discussion within the
industry since Google’s disclosed in October that its six company-built data
centers had an average PUE of 1.21. That benchmark improved to 1.16 in the
fourth quarter, and hit 1.15 percent in the first quarter of 2009, according
to Google’s Chris Malone. The most efficient individual data center
(described as “Data Center E”) has a PUE of 1.12.

“These are standard air-cooled servers, and best practices is what enabled
these results,” said Malone. “What’s encouraging is that we’ve achieved this
through the application of practices that are available to most data centers.
There’s great potential for all data centers to improve their PUE.”

But there’s also some serious Google magic at work. One of the keys to
Google’s extraordinary efficiency is its use of a custom server with a power
supply that integrates a battery, allowing it to function as an
uninterruptible power supply (UPS). The design shifts the UPS and battery
backup functions from the data center into the server cabinet (see our
February 2008 story describing this technology). This design provides Google
with UPS efficiency of 99.9 percent, compared to a top end of 92 to 95
percent for the most efficient facilities using a central UPS.  Malone
addressed the details of how Google measures its PUE, picking up on recent
best practices outlined by The Green Grid. Google measures its power use at
the power distribution unit (PDU), since it has power tracking on the newer
versions of its custom servers, but not all of them. It takes measurements on
a continuous basis in four of its six PUE-rated data centers, and on a daily
basis in the other two.

Malone said he expects Google’s PUE to head even lower. “A reasonable target
can be 1.10,” said Malone, who said Google has designed its new data center
in Belgium to operate without any chillers, which are traditionally the most
energy-hungry pieces of data center gear. Google makes extensive use of free
cooling, which uses outside air rather than air conditioners to keep the
facility cool. But the Belgium site will be the first one to forego chillers
entirely, a tactic that is only possibly in areas with a particular
temperature range.

Urs Holzle, Google’s director of operations, said the growing interest in
data center efficiency was a key factor in Google’s decision to share more
about its operations. “We were really encouraged by the renewed industry
interest,” said Holzle. “There wasn’t much benefit of preaching efficiency
when not many people were interested.

“We’re proud of our results, but the point isn’t where we are, but where
everyone can be,” he added. “We all need to improve our data centers. There’s
a really a lot of low-hanging fruit.”

And then there’s Google’s custom servers and UPS design, which was on
display. Holzle was asked whether he expected to see server vendors introduce
similar designs. “I think the on-board UPS is a natural for many
applications,” he said. “We have patents, including some that have been
published. We’d definitely be willing to license them to vendors.”

We’ll have more updates later today from the afternoon sessions, and much
more coverage in days to come.

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