The physical infrastructure of data centers and network rooms is typically oversized by five times the actual capacity at start-up and more than one and a half times the ultimate actual capacity. The utilization of the physical and power infrastructure in a data center or network room is typically around 50-60%. The unused capacity of data centers and network rooms is an avoidable capital cost, and it also represents avoidable operating costs, including maintenance and energy. In this white paper, the fundamental reasons why oversizing occurs are discussed and an architecture and method for avoiding it is described.