Building the DCO was not without its challenges, however. Besides "playing Tetris with the room" to figure out how best to place equipment, Ganger found that convincing researchers to share was not always easy.

"We learned how hard it is to get people in the same space," says Ganger, who described the project at a recent event hosted by Schneider Electric and in an interview with Network World. "Each group had its own operating system that they had to have, and their own set of libraries and unique setups. Early on it was clear we had to use virtual machines."

Rather than use the expensive VMware virtualization tools, Ganger opted for the open source Xen and KVM platforms. About a third of DCO machines have been virtualized, making it easier to increase and decrease resources provisioned to each research group. Overall, virtualization has been very useful but raised some interesting concerns, he says.

need lots of memory, Ganger notes. If VMs can be suspended when they are not in use, it's easier to provide memory to the VMs that need it. But suspending a VM can harm the application running inside it, if the application wasn't written specifically for a VM, Gagner says.

"If they have open network connections that are active, those connections will break [when the VM is suspended]," Ganger says. "We're trying to figure out how to have the capability to get stuff out of the way so it's not taking up memory."Ganger and his team designed the Data Center Observatory in partnership with the Schneider Electric-owned APC, which supplied In-Row Cooling and Hot Aisle Containment technologies, allowing potential capacity of 40 racks and 774 kilowatts of power.