How does Xen compare to other solutions such as UserMode Linux (UML) and VServer?
UML uses emulated system calls and emulated disk drivers which make it very slow, especially when it comes to context switches and disk I/O. Xen itself is a hypervisor with the base operating system simply being a VM under it. This makes it have very low overhead (2-8%). Linux VServer is a shared kernel with security isolation so it lacks many features such as no low level networking, IPSec, IPv6, iptables, ebtables, loadable kernel modules, etc. Xen is currently the best performing option and is the most like having a physical Linux server. For more information please see our Technology section.
