With 10,000 servers I think one of the things you could do is refresh old hardware. New hardware is vastly more efficient than older hardware. If there's some

With 10,000 servers I think one of the things you could do is refresh old hardware. New hardware is vastly more efficient than older hardware. If there's some place where you can accelerate the refresh, you could find yourself condensing servers. Otherwise, you can factor in future growth with the same number as servers you have now, which is definitely a savings. Consider virtualizing smaller pieces of hardware if you haven't already. Ensure your room has proper airflow. Sometimes air gets stagnant in the corners of the hot or cold rows, resulting in less efficient cooling. Small fans can get the air moving again. You may also need to put fans under your raised floor, or to exhaust waste heat. Taking the back doors off the racks will drop the server temps (particularly in blade racks). That in turn suggests you could run less A/C and bump the temp up to where they were at.