Xen Virtualization Technology The Xen® Hypervisor, is an open source virtualization platform that powers the world’s largest clouds in production and is the foundation of many commercial products. Xen® powers public clouds such as Amazon Web Services, Rackspace Public Cloud and many others. Examples of Xenbased server products include Huawei UVP, Oracle VM and Xen. Examples of client products and appliances include QubesOS, XenClient and Netscaler. Xen is 9 years old, mature and its stability and versatility is second to none. The University of Cambridge Computer Laboratory developed the first versions of Xen. TheXen community develops and maintains Xen as free software, licensed under the GNU General Public License (GPLv2). Xen is currently available for the IA-32, x86-64 and ARM computer architectures. Uses : consolidation leading to increased utilization rapid provisioning dynamic fault tolerance against software failures (through rapid bootstrapping or rebooting) hardware fault tolerance (through migration of a virtual machine to different hardware) the ability to securely separate virtual operating systems the ability to support legacy software as well as new OS instances on the same computer Xen’s support for virtual machine live migration from one host to another allows workload balancing and the avoidance of downtime. Virtualization also has benefits when working on development (including the development of operating systems): running the new system as a guest avoids the need to reboot the physical computer whenever a bug occurs. Sandboxed guest systems can also help in computer-security research, allowing study of the effects of some virus or worm without the possibility of compromising the host system. Finally, hardware appliance vendors may decide to ship their appliance running several guest systems, so as to be able to execute various pieces of software that require different operating systems.