Virtualization vendors not named Microsoft or VMware

Aside from VMware and Microsoft, what other tools can be reliably counted on for virtualization? What are the differences between the products?

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Xensource, Virtual Iron, and Virtuozzo are the big names in the virtualzation space if you are not considering VMWare or Microsoft. Xensource is the commercial provider for Xen, an open-source virtualization platform. Xen uses paravirtualization, so the guest operating system must be modified (i.e. no support for Windows guests) unless you choose to use Xen with "native virtualization" that requires special hardware such as AMD Pacifica or Intel VT.

Virtual Iron is also based on Xen, but has decided against paravirtualization and offers "native virtualization" using hardware-assisted virtualization technology -- limiting the possible servers that can run Virtual Iron. This may or may not be a problem for you depending on your environment.

Virtuozzo forgoes server virtualization altogether, in favor of OS Virtualization. With OS virtualization the operating system is partitioned instead of virtualizing a whole computer. This means that it is not possible to run mixed operating systems on the same host. You must run Linux on Linux and Windows on Windows.

Overall, I believe that Xensource and Virtual Iron offer the most flexibility of the three. However, if you are standardizing on one operating system anyway, Virtuozzo may be an attractive alternative. Either way, competition will be good for the whole virtualization market.

This was first published in January 2007

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