Now back to the Energy Star server requirements: As I noted, they consider only how much electricity a server consumes when it's on but doing no work. Granted, underutilized servers abound in the datacenter, so server power consumption at idle is relevant. However, datacenter operators are becoming increasingly aware of the problem. Organizations are tracking down underutilized machines and employing virtualization to get as much performance per watt as possible from their hardware. Others are dabbling in powering down servers entirely when they're not in use. In short, weighing energy consumption at idle merely scratches the surface of a server's overall power usage.
[ Virtualization was a key tool for reducing energy consumption among 2009 InfoWorld Green 15 winners. ]
Ideally, the Energy Star spec for servers would consider server performance per watt (the equivalent of miles per gallon in cars) at various levels of server utilization: X processes per watt at 25 percent utilization, Y processes per watt at 50 percent utilization, Z processes per watt at 75 percent utilization, and so on.
Of course, that's easy for me to say. There continues to be much debate and, yes, controversy as to the best way to measure performance per watt for servers. SPEC took a stab at it in 2007 with its SPECpower benchmark, which goes much further than Energy Star and still garnered some criticism for being insufficient. Similarly, independent analysts such as Neal Nelson have devised benchmarks for measuring performance per watt -- but thus far, nothing has been fully embraced by the industry. Debate centers around what sort of workloads to measure, where server temperature should fit into the equation, where virtualization functionality fits into the picture, and so on.
Back, though, to Energy Star requirement for servers, Sun's Bapat pointed out another drawback to the program: It doesn't take into account how many cores per processor a machine has. "The fact is, when you go from a server that has four processors with two cores each to two processors with four cores each, you save energy. That's not recognized by the spec," he said. "If you're shipping a server with one processor, it doesn't matter if you have one core or two cores or four or eight. You still get the same idle power allowance. There's no benefit for the fact that you can do, say, eight times work with a fewer number of watts."