With Xen virtualization, a thin software layer known as the Xen hypervisor is inserted between the servers 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.
The Xen hypervisor is a unique open source technology, developed collaboratively by the worlds best engineers at over 20 of the most innovative data center solution vendors, including Intel, AMD, Cisco, Dell, Egenera, HP, IBM, Mellanox, Network Appliance, Novell, Red Hat, SGI, Sun, Unisys, Veritas, Voltaire, and of course, XenSource. Xen is licensed under the GNU General Public License (GPL2).
XEN is part of SUSE Linux 10
Paravirtualization Provides Near-Native Performance
Xen paravirtualization technology is widely acknowledged as the fastest and most secure virtualization software in the industry. Xen offers near-native performance for virtual servers with up to 10 times less overhead than proprietary offerings, and benchmarked overhead of well under 5% in most cases compared to 35% or higher overhead rates for other virtualization technologies.
Xen virtualization quickly becoming open source 'killer app'
