xen

With Xen virtualization, a thin software layer known as the Xen hypervisor is inserted between the server’s hardware and the operating system. This provides an abstraction layer that allows each physical server to run one or more “virtual servers,” effectively decoupling the operating system and its applications from the underlying physical server. Once a virtual server image has been created it can run on any server, at any time, and multiple virtual servers can simultaneously share a single server, increasing its utilization while receiving a resource guarantee that ensures that application layer performance criteria are met.