Energy-efficient servers earn a star -- but so what?

Servers can now earn the U.S. Environmental Protection Agency's Energy Star label in recognition of their green qualities, but most observers aren't expecting this program to cause substantial changes in how enterprises buy servers anytime soon.

The Energy Star server certification went into effect on May 15 and has earned the EPA kudos from manufacturers and users for promoting energy efficiency in an area that's notorious for its high electricity needs.

"This is a great first step. It's been important for some time, given the power issues of the data center, to give transparency on the energy use of servers," says Subodh Bapat, vice president and distinguished engineer in the sustainability office at Sun Microsystems Inc.

But the Energy Star label doesn't tell the full story on servers and their energy consumption. The current specifications measure energy use only under limited circumstances and for specific types of machines. Blade servers, so popular in enterprise data centers, don't qualify, for example. Energy Star specifications vary depending on a number of factors, such as configuration and server size, and certification requires that a server, when idle, cannot exceed certain energy consumption standards for its classification.

What all this means is that while an Energy Star label presumably will help users identify energy-efficient servers, anyone who wants to know more exact figures on their servers' electricity bills will still need to do their own testing and due diligence.

Different types of work

It's not a clean comparison at this point partly because servers are sized differently to do different types of work. Energy Star program officials are working with the server community to find the best way to make better, more direct comparisons between different servers. They're hoping the second version of the program will start to do that. But, even now, Energy Star servers will be in general more energy efficient than non-Energy Star servers, and the fact that they're more efficient in an idle state is important, because many servers are idle for a good portion of the time.

The current Energy Star requirement "is making sure the power supply itself is efficient, but it doesn't focus on the server overall. What it doesn't tell you today is what type of workload you can do for each unit of energy consumed," says Austin Hipes, director of field engineering at Network Engines Inc. (NEI), a Canton, Mass.-based appliance maker.

Instead, the Energy Star server specifications primarily measure whether a server's power supply has good efficiency across a range of workloads, Hipes explains.

That's not to downplay the importance of that information. That kind of efficiency, Hipes says, means that the server's power supply uses a significant portion of the energy it takes from the grid rather than losing a lot of it in the form of heat. (Heat is a big issue in data centers, because generally speaking the hotter the facility the more air conditioning is required to keep servers cool. There has been some counter-intuitive thinking about this in recent years, however.)

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