Spiraling energy consumption has become a major concern for the world's largest Web companies; a report published by McKinsey & Company and the Uptime Institute in July 2008 estimates that datacenter energy usage will quadruple during the next decade in the absence of efforts to improve efficiency.

The pressure to reduce costs and curb emissions is forcing datacenter managers to radically rethink design and management. Google recently built a datacenter in Belgium that relies entirely on ambient cooling--on days when the weather gets to warm, the center's servers are simply shut down. Maggs says that an energy-aware Internet-routing scheme is an extension of this idea. "Resources are getting more fungible and this is the ultimate extension of that," he says.

"In principle this could work," says Jonathan Koomey, a staff scientist at Lawrence Berkeley National Laboratory and a consulting professor at Stanford University, who studies information technology energy use and environmental impact. "The trick is to be able to control these systems well enough and to create controls that are cheap enough to be able to take advantage of the arbitrage opportunity available from differential electricity prices, without affecting reliability or latency," says Koomey.

Maggs cautions that the idea is not guaranteed to reduce energy usage or pollution, only energy costs. "The paper is not about saving energy but about saving cost, although there are some ways to do both," he says. "You have to hope that those are aligned."

Furthermore, he warns that the scheme relies on companies' hardware having some sort of "energy elasticity." In other words, their servers need to use substantially less power when idle than when running full tilt. This has not always been the case, but Google says that its custom servers consume 65 percent of the normal power when idle.

Michael Manos, senior vice president of Digital Realty Trust, a company that designs, builds, and manages large datacenters, believes that the lack of elasticity currently built into modern hardware makes it impossible to achieve the improvements suggested.

"It is great research but there are some base fundamental problems with the initial assumptions, which would prevent the type of savings they present," Manos says. Because most servers aren't used to capacity, he says, "you just can't get there."

However, Manos does see plenty of room for improvement in datacenter designs. "I believe the datacenter industry is just beginning to enter into a Renaissance of sorts," he says. "Technology, economic factors, and a new breed of datacenter managers are forcing change into the industry. It's a great time to be involved."

Koomey suggests that spiraling energy costs could encourage some companies to consider radical steps such as rerouting data: "Electricity use is a big enough component of data-center costs that this just might work."