If market-leading VMware, open-source incumbent Xen, and Microsoft's upcoming Hyper-V aren't enough choices, another server virtualisation product is on the way: Parallels Server.

SWsoft, which is in the process of renaming itself Parallels, released its first beta version of the server virtualisation software Wednesday. SWsoft itself has chiefly focused on commercializing higher-level virtualisation software called Virtuozzo that lets a single version of an operating system be subdivided into semi-independent containers. However, the company's Parallels division has come to prominence by letting a single computer--most notably an Intel-based Apple machine--run Windows.

That Parallels technology is now available as a hypervisor that runs on a computer's "bare metal," a contrast to the previous technology that runs on top of a host operating system such as Mac OS X. The hypervisor approach, also employed by VMware's ESX Server, Xen, and Hyper-V, is generally preferred for servers to the guest-host model.

Parallels Server's claim to fame over its rivals is its ability to run multiple versions of Mac OS X, and it's "the first to run multiple copies of Mac OS X Server on a single Apple computer," the company said. The server beta also is the first hypervisor to support Intel's second-generation VT-d virtualisation hardware, though it's still at the experimental level, the company said.

Those are interesting accomplishments, but they don't seem to me to be the competitive breakthroughs that will dent VMware's prevailing dominance. Apple's Xserve machines account for only a tiny slice of that market compared with those running Windows and Linux, and support for the latest Intel hardware doubtless will spread to rival hypervisors.

So it's probably a good thing for SWsoft/Parallels that it also has its Parallels desktop, Virtuozzo, and virtualisation management software lines up and running. Parallels Server could well appeal to the sizable number of customers who already have Virtuozzo and accompanying management tools installed. Those folks might want to expand into new virtualisation territory. To take one niche where Virtuozzo found early success, Web site hosting companies could offer more independent partitions to customers who are sharing a server.

Those who wish to test the Parallels Server beta software can apply at SWsoft's Web site.