The beauty of the system, Xiao says, comes when the two systems work in tandem. The sensors monitor the servers to make sure they’re not being overcooled (a common problem in data centers, he says, since people often set the cooling system conservatively, to protect the equipment). In addition, the sensor system watches for hot spots, which can make the air-conditioning system work inefficiently. This information is then used by the load-skewing algorithms. Knowing that you want to shut down 400 servers is one thing. The sensor helps determine which ones to shut down.
Jonathan Koomey, a staff scientist at Lawrence Berkeley National Laboratory and the author of several reports on data-center energy consumption, says that he sees this type of research as one step toward a big-picture vision for data centers. “There’s a focus by the big players in the data-center area to try to get to a point where they can shift computing loads around, dependent on not just electricity prices, but also weather and other variations.” Ultimately, Koomey says, this could mean shifting loads not only within a data center, but also from region to region.
The group ran simulations using data from the IM service Windows Live Messenger and found that the system could produce about 30 percent in energy savings, depending on the physical structure of the data center and on how the system is configured. Zhao says that the savings produced by the group’s system does depend on how the user chooses to deal with some inherent trade-offs. For example, he says, Microsoft is working on several areas of research that will help in modeling the unexpected, such as load spikes. However, a user might choose to keep more servers than is strictly necessary powered on as a reserve in case of a spike, at a corresponding loss in energy savings. “Our research shows the trade-off between energy saving and performance hit, and lets users choose the right balance,” Zhao says.
Other researchers are working on developing techniques for shutting down servers at optimal times. Xiao says that the Microsoft group’s work is distinguished by its focus on connection servers and the problems that come with shifting loads when users typically stay logged in for many hours.
“Servers are only being used [about] 15 percent of their maximum computing ability, on average,” Koomey says, “so that means a lot of capital sitting around.” He expects companies to be very motivated to implement the research that they do in this area, since “they want to make better use of their capital,” he says. Wasting energy and computing power doesn’t make good business sense.