How Google and Yahoo improved data center energy efficiency
Running large data centers is expensive and getting worse. No one knows that more than Google and Yahoo. At a panel on green data centers at MIT’s Emerging Technologies Conference this week, Yahoo’s senior director of data center engineering and operations, Scott Noteboom, described how Yahoo has grown its server plant by 12 times since 2005. Google’s head of data center research and development, Chris Malone, explained that Google has had to come up with its own server designs to accommodate the ultra-high densities of their data centers. Both have a maniacal focus on improving data center energy efficiency.
Yet both firms are doing things that ordinary enterprises can learn from:
1. Reconsider your business continuity plan. Yahoo is eliminating UPSes and backup generators. Instead, they are architecting each data center as a backup to the others. That eliminates UPSes as a significant power loss. They’ve had to install software that restarts servers in a controlled fashion after power resumes, however. Google took a different tack: eliminating larger UPSes in favor of small battery backups on each server motherboard. Either way, both data center approaches yield significantly greater energy efficiency.
2. Consider the weather when you site a data center. Yahoo is no longer building raised-floor data centers. By locating in more moderate climes, they’re able to utilize prebuilt warehouse-type buildings that use extensive ground-level air intake of cooler ambient air and roof-level exhaust of hot air.
3. Raise the temperature and humidity. Modern servers can run warmer and moister than you might think. A lot of conventional wisdom about server environments stems from the mainframe days, when you didn’t want punch cards wilting.
4. The big win in facilities power reduction in the data center is in cooling. Malone points out that typical chiller systems are only 60% efficient; Google has gotten to 90% by switching to evaporative cooling. Focusing on electrical transmission issues is good but yields much less improvement.
Google and Yahoo make extensive use of virtualization to improve capacity utilization and reduce the overall load. Noteboom and Malone stressed that senior IT managers need to make these issues part of the discussion with system architects, project managers and developers. All too often, those folks start from the premise of buying a certain kind of server for a certain kind of app, rather than asking how existing capacity could be deployed to meet that need.
And the result of all those efforts at Google and Yahoo? Dramatic improvements in power efficiency. The typical metric for this is power utilization efficiency, which means the ratio of total power consumed by the data center to total power consumed by just the servers themselves. Most contemporary data centers are in the 2.0-2.5 range – for every watt of power that a server uses to compute, they burn more than a watt in transmission loss, battery loss and cooling. Google is at 1.19 and Yahoo is targeting 1.03 in its next-gen data centers. In other words, if you’re typical, you’re spending twice what they are on power per server.