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Xen virtual machine monitor Computer Laboratory > Systems Resear
ch Group > NetOS > Xen virtual machine monitor  The Xen™ virtual
machine monitor  Modern computers are sufficiently powerful to
use virtualization to present the illusion of many smaller
virtual machines (VMs), each running a separate operating system
instance. Successful partitioning of a machine to support the
concurrent execution of multiple operating systems poses several
challenges. Firstly, virtual machines must be isolated from one
another: it is not acceptable for the execution of one to
adversely affect the performance of another. This is
particularly true when virtual machines are owned by mutually
untrusting users. Secondly, it is necessary to support a variety
of different operating systems to accommodate the heterogeneity
of popular applications. Thirdly, the performance overhead
introduced by virtualization should be small.  Xen™ is a virtual
machine monitor for x86 th