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Where Will Open Source Go Next?

Companies looking to squeeze more out of their IT infrastructure investments have for years been able to build virtual servers within mainframe, Unix, and even Windows environments. A movement to deliver this capability to Linux environments is gaining momentum thanks to Xen hypervisor, an open-source software virtualization tool managed by a startup XenSource Inc. and backed by some of IT's biggest vendors.

Advanced Micro Devices Inc. and Intel are developing 64-bit processors that will make use of Xen hypervisor, while Linux providers Novell and Red Hat are working with XenSource to provide support for users consolidating server environments. Hewlett-Packard and IBM are contributing code to the Xen project and working with XenSource to develop new uses for the technology.

XenSource in January launched with a $6 million round of funding led by Kleiner Perkins Caufield & Byers and Sevin Rosen Funds. To succeed, they'll have to take on well-established competitors, since Microsoft and VMware, a subsidiary of storage maker EMC, offer proprietary software that can be used to create virtual servers on Intel or AMD x86-based servers. Yet in a market where business-software buyers increasingly welcome an open-source alternative, XenSource could find an opening. "[Xen] is still very immature, but it offers a lot of promise that will be realized by first by Linux users and then in other environments," predicts IDC analyst Dan Kusnetzky.

Xen, which is licensed under the GNU General Public License, works on servers running any open-source operating system, including Linux and NetBSD, with ports to FreeBSD and Plan 9 under development. When Intel and AMD deliver new processors within the next year that support virtual servers on the chip level, Xen should be able to run on proprietary operating systems as well.

A more subtle difference between the Xen hypervisor and competing proprietary technologies is that Xen keeps cache memory that records the state of each virtual server and operating system. XenSource does this through "para-virtualization," or splitting the operating-system drivers in half. By doing this, one half operates the virtual server while the other half can be kept as a separate domain where this cache memory can be stored. "This saves users time and resources when switching between virtual servers," says Simon Crosby, VP of strategy and corporate development for XenSource.

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