Greening of Data Centers Spurred by New Metrics
May 09 , 2011
"How Green Was My Valley" was a best-selling, coming-of-age novel about life in a Welsh mining town that was made into a popular movie.
"How green was my data center" isn't likely to come to the big screen, but it is just as intriguing for environmentally-conscious CIOs. And it proves to be an extremely complicated question.
Government and industry are pushing to develop metrics that will state definitively whether a data center is energy efficient or not. Ideally, they would like to get some generally-accepted measures, equivalent to the auto industry's miles-per-gallon standards that make it clear how efficiently a particular data center uses energy.
"There is a long way to go to achieve 'the Holy Grail,' the measurement of 'useful work per kilowatt hour.'"
In a major breakthrough in February, government agencies in the U.S., Europe and Japan agreed they would recommend that an industry measure called Power Usage Effectiveness be used as a worldwide standard. PUE was developed by the Green Grid Association, a Portland, Ore.-based group of IT vendors and users that promotes resource efficiency in data centers and business computing ecosystems.
Roger Tipley, vice president of Green Grid, said the governmental approval "validates our role as a trusted advisor." Still, he says, there is a long way to go to achieve "the Holy Grail" which would be a measure of "useful work per kilowatt hour." One proxy for efficiency that Green Grid is evaluating is the bits per second traveling through the network. Another is utilization of servers.
The PUE measures energy overhead. It is a ratio that compares the amount of energy used in a data center to power servers, switches and storage devices to the total amount of energy used, including what's needed to distribute power, air condition the facility and run the machines. The goal is to optimize data centers so that almost all the power is dedicated to powering servers, switches and disk drives. A perfectly efficient datacenter would have a PUE very close to 1, while the average for data centers today is about 2, Green Grid says.
The government approval was a result of work by the Global Metrics Harmonization Task Force on measurement protocols. The name sounds like a New Age association to study crystals and convergence, but it is actually comprised of engineers and policy wonks. They come from agencies like the U.S. Environmental Protection Agency and Energy Department, Japan's Economy, Trade and Industry ministry and its Green IT Promotion Council, and a European Community research center studying data centers.
Establishing standards for efficiency in data centers is becoming increasingly important. In 2007, the EPA estimated that data centers were using 1.5% of America's electric power and would be using 3% by 2011 if growth trends continued. McKinsey said that annual worldwide data-center carbon-dioxide emissions were comparable to those of Argentina.
But the combination of new technology and higher electricity prices are helping reduce energy use by data centers. The biggest single change is the move to consolidate data centers and move applications and infrastructure to the cloud. Big, purpose-designed, stand-alone data centers can be much more efficient than smaller data centers located inside general-purpose office buildings.
And cloud architecture with virtualized servers dramatically increases the work run on each server, increasing efficiency. Before the age of virtualization, it was common to have one server handle each application, with each server running at 10% of capacity. Some data centers had numerous "ghost servers" that kept humming away long after the project for which they were purchased had been cancelled.
Companies building new data centers are achieving dramatic results. Google, Facebook and Cisco have all achieved PUE numbers approaching " 1."
The need to reduce electric power use has made data center operators much more conscious of air-flow, and architects are careful to position racks of servers to avoid "hot spots" that require excessive cooling. Advice columns tell managers to take advantage of outside air for cooling when temperatures fall and to cover over holes in raised floors where cool air dissipates.
Facebook, for example, places batteries for backup power near servers, rather than in a separate battery room, to minimize power transmission losses. The company cools the plant by letting air from the outside flow over foam pads moistened by water sprays. Cisco's newest data center can use ambient fresh air up to 75 degrees before the air has to be chilled, which it calculates will be 65 percent of the time. If the power fails, instead of hundreds of batteries for backup power it uses rotary flywheels to run generators until the backup diesel engines can be started up; roof-top solar cells power offices in the building.
Such gains and the promise of cloud computing, led clean-tech analysts Pike Research to predict that data center's worldwide energy use will be 38% lower than expected by 2020. That drop will contribute to a decline in total data center energy costs to $16 billion in 2020 from $23.3 billion in 2010. Pike predicts the decline will also reduce greenhouse gas emissions by 28%.
Still, measuring the environmental impact of data centers requires more study. Green Grid says it is working on metrics to relate the use of water by a facility to its useful work produced. It also is working on measures that reflect whether the center is powered by carbon-dioxide-emitting fossil fuels or by clean, renewable energy sources.
The U.S. EPA has applied its EnergyStar rating system to evaluate the efficiency of data center servers. Now it is working on ratings for storage boxes and network switches.
Katherin Winkler, secretary of Green Grid, says that even if data center energy use creeps up as a percentage of world wide energy use, it may not be a bad thing. She points to studies that show that "because of the growing role that IT plays in making other sectors more efficient, there can be an overall carbon reduction by using more IT."
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