Linux Virtual Machines with Xen
Sean Reifschneider
What is Xen
Virtual Machine Monitor
Multiple virtual machines on one computer
Similar to VMWare or User Mode Linux or IBM S390
Very fast
Originated at University of Cambridge
XenSource
Uses for Xen?
Useful for building packages for multiple targets
Crash and burn machines are very easy
Partitioning machines by application for security
Hosting of small applications
Trying out new software or distributions
Demo machines
VPN hub machine
Hardware Support
Supports 32-bit and 64-bit systems.
Recently added support for SMP guests.
Some recent CPUs from Intel and AMD support enhancements
Unique features
Balloon driver to scale memory use
Save/restore virtual machines
Live migration
Performance
Worst case: Xen is 8% slower than native
UML and VMWare are as much as 88% slower
Up to 128 virtual machines supported
Behind the Scenes
Boot up Xen hypervisor
It loads the "xen0" guest
xen0 has direct access to the hardware
xen0 can create and control many xenU guests
xenU guests see partitioned environment
Device access proxied through xen0
Guest network typically bridged to host Ethernet
Demo
Setup on FC6
Packages are in FC6 and SuSE, Debian Testing
yum install xen
Reboot into Xen and Xen0
Create your virtual machines
OS Support
OSs have to be ported to Xen
Linux 2.4 and 2.6
NetBSD-current
FreeBSD 5 (guest only)
Plan 9 (guest only)
ReactOS (in development)
Support for unmodified guests on VT hardware