Virtualization is the technique of running a "guest" operating system inside an already-running OS - for example, Windows inside Linux, or visa-versa. This article compares four virtualization products available for Ubuntu Linux: the free, open source Qemu; the closed-but-free versions of VirtualBox and VMware-Server, and the commercial Parallels.

The findings were interesting - the only product that requires the purchase of a licence for personal use, Parallels, actually performed the worst of the group. Qemu did well for a completely free-as-in-speech application, although VMware and VirtualBox blew the competition away in terms of performance. Of these applications, VMware and VirtualBox definitely come out the clear winners. For individual use, where the ability to run a single Windows desktop inside of Linux is all that is needed, VirtualBox turns out to be my preference. It's much smaller than VMware, which comes packed with extra features that aren't necesary for the end-user. If your needs are different, however, you'll probably want to give VMware a closer look. Overall, the maturaty and stability of all four applications was impressive enough to call virtualization on the Linux desktop "complete."