Virtualization and Linux--A Primer - page 3
Why the Hooplah?
But there are some obvious performance and security questions in such a setup. How much of a load can a system realistically handle? What if the whole works goes down because of a successful intrusion, runaway process, or some other system-wide catastrophe? What if someone just loads up the whole works into a van and drives it away? What if it's so freaking complex and difficult to administer you give up and retire to a hermitage?
VMWare is the current champion of virtualization on x86. Software developers have long used VMWare on workstations, because it let them keep their nice Sun pizza boxes even as they were forced to interact with, or even worse, develop for Windows. While VMWare is a nice polished application, it carries a heavy performance price and requires some pretty stout hardware in order to function with a reasonable amount of peppiness. This is because all the work is done entirely in software. In contrast, the VM operating system runs on specialized hardware that handles the bulk of the virtualization load, so it delivers great performance.
But the times they are a a-changing, and there are two reasons why virtualization is suddenly all the rage: Xen, and x86 hardware support for virtualization.