Linux Virtualization Technologies Compared

Linux supports multiple open-source technologies for virtualization, the most
popular being Xen, KVM, OpenVZ and Vservers. Each has its strengths, weaknesses
and tradeoffs, so selecting the right one for your environment is non-trivial.

This talk will cover the capabilities of the four major virtualization types,
in the following areas.

Resource use : All methods of virtualization impose an overhead in addition to
the cost of processes running within each virtual machine. However, this
overhead varies between KVM (the most expensive) and OpenVZ (the cheapest).

Isolation : Virtual machines should be ideally isolated from each other and
from the host system, and be limited in the amount of CPU, RAM, disk space
and network bandwidth they can use. However, in practice the level of isolation
depends on the technology used - Xen performs with best, Vservers the worst.

Manageability : A good virtualization technology makes it easy to create,
manage, move and destroy virtual systems. Each of the four types has its
own tools, commands and configuration file format.

Flexibility : Some virtualization methods like OpenVZ and Vservers can only
run Linux, while others like Xen and KVM can run almost any operating system,
if they have the required hardware support.

Future support : Each technology is developed by different groups, and not all
are as well maintained. KVM is the leader here, as it is now part of the Linux
kernel, while Vservers seems to be falling behind.