Efficient UPS Aids Google's Extreme PUE

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.