Screaming Penguin

DeveloperWorks has a good article on Xen, the new OS virtualization package for Linux.

Virtualization is often used to separate (or "sandbox") applications and systems from the others on the same hardware. Linux supports many different forms of virtualization ranging from hardware emulators to pure hardware virtualization. One recent standout in the growing list of virtualization technologies is Xen, developed at the University of Cambridge. Xen is noteworthy because of its unprecedented performance and security. Along came Xen Developed as a research project at the University of Cambridge, Xen has gained a lot of momentum in the open source community. Xen is a paravirtualizing VMM (Virtual Machine Monitor), meaning that the operating system is modified in select areas to make calls into the hypervisor, whereas the applications that run on that operating system are unmodified. While other virtualization systems like VMWare demonstrate true virtualization (in which they don't have to modify the running operating systems), they still need to do on-the-fly translation of the machine code, which can affect performance. Because Xen requires a modified operating system, you cannot just take a current Linux kernel and run it under the Xen hypervisor unless it is ported to the Xen architecture. However, if the current system can use a new Linux kernel that has been ported to the Xen architecture, you can run your existing system without change.

A lot of that excitement in the community, though, is that Xen may one day become a product that provides real server partitioning under Linux, and replaces not just little test beds, but things like the VMWare server product.