George Mason University
Virtualization was invented more than thirty years ago to allow large expensive mainframes to be easily shared among different application environments. As hardware prices went down, the need for virtualization faded away. More recently, virtualization at all levels (system, storage, and network) became important again as a way to improve system security, reliability and availability, reduce costs, and provide greater flexibility. Virtualization is being used to support server consolidation efforts. In that case, many virtual machines running different application environments share the same hardware resources.