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Virtualization, Hypervisors and Xen[1][2] - Muli Ben Yehuda


Topics to be covered include a general introduction, design and implementation of Xen, the new Xen 2.0 IO model and future plans.

[2] A short overview of Xen, from

Xen is a virtual machine monitor, developed by the University of Cambridge Computer Laboratory. Unlike VMWare, which provides complete virtualization, guest operating systems need to be ported to the Xen environment. So far, Linux 2.4 and 2.6 have been ported, as well as NetBSD, FreeBSD and Plan9, and Windows XP. The Windows XP port was done in collaboration with MS Research, and took much longer than the Linux port...

Xen works by letting the monitor (hypervisor) run in ring 0, and the guest OS run in ring 1. Userspace runs in ring 3, as usual. From a Linux point of view, porting Linux to Xen (refereed to as XenoLinux) is just a matter of implementing the arch specific hooks in Linux - no core kernel files are modified!

Xen provides secure protection between VMs (unlike e.g. coLinux), allows flexible partitioning of resources, and supports seamless low-latency migration of running VMs(!). They also claims impressive performance numbers, within 3% of the host performance.

Lecture slides (PDF format)

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