Information AboutXen |
| CATEGORIES ABOUT XEN | |
| free virtualization software | |
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name = Xen
Xen is an Open-source Virtual Machine Monitor , or Hypervisor , developed by the University Of Cambridge . It has a design goal of being able to run 100 full-featured Operating System (OS) instances on a single typical computer. Xen provides secure isolation, resource control, quality-of-service guarantees, and live migration of virtual machines. Operating systems must be explicitly modified ("ported") to run on Xen (although compatibility is maintained for user applications). This enables Xen to achieve high-performance virtualization without special hardware support. USE Virtual machines are often used by IBM , HP , and others on mainframes and servers. The primary benefits to virtualization include extracting the most work possible from a single machine, and securing software programs through the use of separate virtual operating systems (similar to using a Chroot Jail , but more secure.) Virtualisation can also be used to run different and incompatible operating systems on the same computer. Xen's support for virtual machine live migration allows workload balancing and the avoidance of downtime. COMPARISON WITH OTHER VIRTUAL MACHINE MANAGER S (VMMS)
PARAVIRTUALIZATION WITH XEN Xen uses a technique called showed a port of NetWare to Xen. A Windows XP port was carried out during the initial development of Xen, but Microsoft's licensing prevents its public release. Sun Microsystems is also actively working on a port of Solaris to Xen. FULL VIRTUALIZATION WITH XEN Intel has contributed modifications to Xen to support their VT-X Vanderpool architecture extensions. This technology will enable unmodified guest operating systems to run within Xen virtual machines, if the host system supports the Vanderpool or the Pacifica extensions (Intel's, and AMD's, respectively, extensions to natively support virtualization). Practically, this will mean that there will be a performance boost, and that it will be possible to virtualise Windows without having to modify it in any way, which licensing restrictions prevent. VIRTUAL MACHINE MIGRATION Xen virtual machines can be "live migrated" between physical hosts without stopping them. During this procedure, the memory of the virtual machine is iteratively copied to the destination without stopping its execution. A very brief stoppage of around 60–300 ms is required to perform final synchronisation before the virtual machine begins executing at its final destination, providing an illusion of seamless migration. Similar technology is used to suspend running virtual machines to disk and switch to another virtual machine, and resume the first virtual machine at a later date. HARDWARE ARCHITECTURES Xen currently runs on X86 , with P6 or newer processors, and X86_64 based systems. Ports are currently underway to IA64 and PPC . Ports for other platforms are also technically possible and may be available in the future. SOFTWARE PLATFORMS Xen mainly runs with Linux as a host system and is the most supported platform. FreeBSD/NetBSD can also be used as FreeBSD 7-CURRENT (and 6-STABLE) supports the latest Xen version (version 3); NetBSD 3.0 can run Xen 2, an older version, although NetBSD-current also can run Xen 3. It's currently possible to run Windows as a guest operating system unmodified, using hardware virtualization provided by Intel's Vanderpool technology (only available in recent processors) or the upcoming AMD Pacifica. It is however impossible to use Xen on top of a Windows host. {Link without Title} Xen in Unix-like systems also includes Xen packages, in unstable and experimentals. NetBSD 2.0 includes support for Xen 1.2, NetBSD 3.0 release includes support for Xen 2.0. Support for Xen 3.0 is available in NetBSD-current. FreeBSD 6.1 will have full support for Xen 3 on x86. SEE ALSO
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