Xen

The Xen® hypervisor, the powerful open source industry standard for virtualization, offers a powerful, efficient, and secure feature set for virtualization of x86, x86_64, IA64, PowerPC, and other CPU architectures. It supports a wide range of guest operating systems including Windows®, Linux®, Solaris®, and various versions of the BSD operating systems.

Server Virtualization with the Xen Hypervisor
Enterprises looking to increase server utilization, consolidate server farms, reduce complexity, and decrease total cost of ownership are embracing server virtualization. The Xen® hypervisor is the fastest and most secure infrastructure virtualization solution available today, supporting a wide range of guest operating systems including Windows®, Linux®, Solaris®, and various versions of the BSD operating systems.

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.

The Xen hypervisor is a unique open source technology, developed collaboratively by the Xen community and engineers at over 20 of the most innovative data center solution vendors, including AMD, Cisco, Dell, HP, IBM, Intel, Mellanox, Network Appliance, Novell, Red Hat, SGI, Sun, Unisys, Veritas, Voltaire, and Citrix. Xen is licensed under the GNU General Public License (GPL2) and is available at no charge in both source and object format. Xen is, and always will be, open sourced, uniting the industry and the Xen ecosystem to speed the adoption of virtualization in the enterprise.

The Xen hypervisor is also exceptionally lean-- less than 150,000 lines of code. That translates to extremely low overhead and near-native performance for guests. Xen re-uses existing device drivers (both closed and open source) from Linux, making device management easy. Moreover Xen is robust to device driver failure and protects both guests and the hypervisor from faulty or malicious drivers.

Xen 3.3 Datasheet

Paravirtualization Provides Near-Native Performance
Xen’s 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.