"Zombie" Servers and Inefficiency Drive Energy Waste at Data Centers

U.S. server facilities are riddled with underused machines, report says.

An employee checks server racks at a data center in Germany. Worldwide, data centers use vast amounts of energy; a new report focuses on inefficiencies at United States facilities.


In nearly 3 million data centers across the United States, some 12 million machines serve up the emails, web pages, and files we access online every day. They're the repositories of all our computerized information.

The high energy demand of those servers is well documented, but up to 30 percent of them are drawing power without actually doing anything.

These "zombie," or comatose, servers are among the examples of energy waste documented in a report about U.S. data centers released Tuesday by the Natural Resources Defense Council (NRDC). If those facilities were to cut electricity consumption by 40 percent—half of what is possible using the tools now available to improve efficiency—the electricity savings would amount to $3.8 billion and 39 billion kilowatt-hours, according to the report.

That's enough to power 3.5 million American homes.

Large companies such as Google, Facebook, eBay, and Microsoft are already highly efficient, a result of major resources and huge scale, but their share of electricity use is just 5 percent of total data center consumption in the United States.

"Our concern is more about the other 95 percent," said Pierre Delforge, who co-authored the new report, which focuses on corporate data centers, small- and mid-size server rooms, and firms that manage data for a variety of clients, which are called multi-tenant data centers.

Underworked Servers

One of the main ways that data centers use energy is to keep all those large, humming server machines cool. The industry has made significant progress in this area, some using upgraded systems that can generate power from waste heat or use outside air in cooler climates. (See related stories: "KPMG Captures Heat for Data Center Cooling" and "National Snow and Ice Data Center Gets Cool Makeover")

But how the machines themselves are being operated leaves a lot of room for improvement, the report finds. That millions of servers are running at only 10 to 15 percent capacity—or, in the case of zombie servers, at zero, is "one of the lesser known issues," Delforge said.

Useless servers tend to stay powered up because no one is aware of them, or no one wants to take the risk of unplugging them in case they are wanted at some point down the road. "It's like an airline flying 30 percent of its planes empty, and the rest of its fleet with an average of less than 15 percent of its seats filled," Delforge said. But as the report notes, data center managers tend not to get in trouble for keeping comatose servers online—their job is to make sure servers don't go down.

The NRDC report highlights the fact that at many data centers, the people managing the equipment are focused on keeping data secure and functioning properly. The electric bill goes somewhere else: a different department at the same company, perhaps, or to the external customer in the case of a multi-tenant data center.

Bill Tschudi, who has worked for about 15 years on data center efficiency and leads those efforts at the Lawrence Berkeley National Lab, said the larger Internet companies have made a lot of advances in recent years.

"But then you look at the rest of the market, and there's been no progress," he said, noting that smaller data centers in particular lack the resources and expertise to make significant changes. "That part of the market really needs to be reached. People are operating the way they were ten or 15 years ago, and the industry's kind of moved on since then."

Many small companies "are not even aware that their server room is a large energy hog and might be responsible for 30 to 50 percent of the entire electricity bill," Delforge said. "It's just not the top of the priority list."

Similarly, companies that outsource to multi-tenant data centers likely have no idea how electricity use factors into the bill, instead paying a flat fee for a block of server space. Most data centers are not disclosing to customers—or anyone else—how much energy they use, Delforge said.

Overcoming the "Fear Factor"

IO, a Phoenix-based multi-tenant data center provider that contributed information to the NRDC report, has designed systems that allow it to measure energy efficiency in real time.

"Energy inefficiency is money left on the table," said Patrick Flynn, group leader of applied intelligence and sustainability at IO. "Why somebody would leave it there means that there must be some nuanced barrier to adopting that change. We see that in the data center world."

Part of the barrier is a lack of insight at many facilities into just how much inefficiency there is. The industry has no agreed-upon standard for gauging how hard a server is working. Setting a simple metric for server utilization, and disclosing the figures, the NRDC report argues, would "help resolve one of the biggest efficiency issues in data centers: underutilization of servers."

At many data centers, aversion to risk can make managers wary of trying new things. "The fear factor in the data center world is that if you're operating OK now, don't change anything because you could upset the systems, and if some systems go down, then somebody's going to get fired," said Tschudi.

The NRDC recommends that data centers set common goals for efficiency among corporate executives and information technology managers alike. It also advocates for more investment in efficient equipment, pricing models that include incentives for efficiency, and more integration of renewable energy, a point also made in a Greenpeace report on data centers released in April. "This is a complex issue," Delforge said. "There is no silver bullet."

IO's Flynn said that the data center sector has been "left behind" on efficiency even as it has helped streamline other industries such as airlines and healthcare. His firm is building energy savings into its business strategy, aiming to compete by offering its clients more visibility into how much energy their servers are consuming and where they might maximize efficiency. "We've got a strategy of passing savings on to customers," he said.

Delforge echoed the idea that data centers have lagged in the productivity and efficiency that they have enabled in other sectors. "We want to make sure that this is not perceived as 'data centers are bad,' " he said. "For data centers to be part of the solution in terms of having a more efficient economy, they need to start cutting the waste in their own backyard."

The story is part of a special series that explores energy issues. For more, visit The Great Energy Challenge.