Inside Extreme Scale Tech|Thursday, December 18, 2014
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How Google Cools Its Data Centers 

Like Apple, Google thrives on doing things differently. Another way to put it is that Google executives and engineers don’t care how everyone else does things, they’re sure they can do better. The designs of the company’s datacenters are a perfect example of that attitude.

Google is obsessed with efficient datacenters, not only to keep costs down and servers up and running, but to keep its environmental impact small. It packs tens of thousands of servers into racks, and has devised a cooling system to make that possible. At Data Center Knowledge, Rich Miller talked to Joe Kava, Senior Director of Data Centers at Google, to find out how it’s done.

Enclosed hot aisle at a Google data center  

The entire room serves as the cold aisle for the servers—if you can consider 270C (800F) to be cold. The hot aisles are enclosed structures sandwiched between the racks. Stainless steel pipes carry water back and forth between the cooling towers and the hot aisles and through cooling coils on the ceilings of the hot aisles. There’s a raised floor but no perforated tiles.

Fans blow the heated air from the servers into the hot aisle enclosures, which reach 490C. The air rises to the top of the chamber, through the cooling coils, and is then exhausted out the top of the aisle back into the server room.

Kava has no fears about leaks from water-cooled coils and pipes. Kava assures us that small leaks in the coils would drip straight onto the raised floor, not on the equipment. Leak detectors and fail-safes keep an eye out for more serious problems. “We have a lot of history and experience with this design, and we’ve never had a major leak,” he says.

And if you’re interested in another approach to water cooling at Google datacenters, check out Steven Levy’s article in Wired about Google’s Finland Data Center.

Google found a recently closed pulp mill in Hamina, Finland with a sea water tunnel running under the floor. Before pulping the logs, the pulp mill had removed bark from them, then burned the bark in huge turbines that generated electricity—a sort of cogeneration of its own. The sea water was used to cool the turbines.

Google installed 30-foot-high pumps to send the water into its own custom-designed heat exchangers, where it cools down fresh water coming from pipes circulating through from the server rooms. The heat exchangers are huge containers with hundreds of ultra-thin titanium plates that keep the sea water separated from the fresh water. And just to make sure, they’re being ultra-environmentally sound, the sea water is cooled back down to 250C before it’s returned to the ocean.

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