Xen Hypervisor: The Future of Enterprise IT?

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At what point does a “standardized” solution become “the industry standard”?

Simon Crosby, CTO at XenSource, has begun calling Xen the “de facto standard” hypervisor for virtualization—despite the fact that enterprise-ready Xen solutions have spent just months in the market and as yet have virtually no market share.

Those with less monetary interest in its success don’t call Xen the standard, but do admit that it has a good chance for widespread adoption. Gartner analyst George Weiss says that while Xen “looks good,” it’s a little bit “presumptuous” for vendors to tout it as the standard at this point.

In the next year or two, Xen proponents will have the opportunity to prove its worth as enterprises begin more widespread adoption of virtualization.

Virtualization 101

At its simplest, virtualization allows users to run more than one operating system on one machine. “Virtual infrastructure is better than real,” notes Alex Vasilevsky, VP and CTO at Virtual Iron. “You can do some truly amazing things on it.” Those amazing things include improving resource allocation, live migration of applications from one server to another, and offering developers a safer environment for debugging and testing new products.

While not all virtualization solutions work in the same way, the vast majority rely on a thin piece of software known as a hypervisor. The hypervisor sits on top of the primary operating system and allocates resources to the guest operating systems. Vendors XenSource and Virtual Iron use the open-source Xen hypervisor, while Microsoft and market leader VMWare developed their own hypervisors.

Currently, a very small percentage of the enterprise data center is virtualized—somewhere between five and ten percent of x86 servers, depending on which survey you read. Few enterprises have invested in virtualization because the previously available solutions (primarily VMWare) imposed a high performance toll and used costly, privately licensed technology. Xen solutions are both faster and less expensive, but they require modifications to the guest OS source code—something that Microsoft, for one, has been reluctant to allow.

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Changes on the Horizon

However, all that is changing with the introduction of the Intel VT-x technology and AMD’s soon-to-be-launched Pacifica chips. These new processors integrate virtualization capabilities directly into the hardware. The new chips do not provide any benefit for VMWare, but they do improve performance for Xen-based solutions and eliminate the need to alter OS code.

“Today virtualization is slow and expensive,” notes Virtual Iron’s Vasilevsky. “Slow is fixed by Xen and the new chips. Virtual Iron addresses the expensive.”

While experts disagree on how quickly enterprises will rush to adopt virtualization, nearly everyone believes that the new chips will speed deployment. Having an industry-standard hypervisor could further speed the growth of the market and move the focus to virtualization management products. “Eventually the talk about which hypervisor is best will die off, and the talk will be about which management tools are the best,” predicts Vasilevsky.

XenSource’s Crosby adds, “Once the hypervisor is a given, we can get into much more interesting development.”

Gartner’s Weiss also sees standardization as the wave of the future, pointing to the recent announcement by Novell and Microsoft as an example. “There is already a recognition that it is senseless to continue to battle each other where standards could grow the market,” he says.

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Xen’s Strong Points

Xen has several advantages that make it the front-runner in the race to become the hypervisor standard. First, its code base contains just over 40,000 lines, so it imposes a very light burden on overall performance.

Second, Xen has attracted the support of a large number of industry heavyweights. It’s already included in Red Hat Enterprise Linux 5, Novell’s SUSE Enterprise Linux 10, and Fedora Core 5. In addition, Intel, IBM, Microsoft, and Sun Microsystems have all announced various levels of support for the technology.

Finally, Xen is cheap. The standalone hypervisor is available for free, and Xen-based management tools are considerably less expensive than those from market leader VMWare.

Crosby sums up Xen’s advantages over their primary competition, asserting, “Currently, Xen has 80% of the features, 120% of the performance, and 20% of the price of VMWare.”

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With a resume like that, how could Xen fail to succeed in its bid to become the hypervisor of choice for the enterprise? In a word, VMWare.

Gartner’s Weiss notes, “The idea that all of VMWare’s installed base will convert to Xen is problematic. VMWare is not just going to disappear.”

Some estimates place VMWare’s market share as high as 50%, and the company shows no signs of slowing growth. According to company releases, in the third quarter of 2006, VMWare’s revenues totaled $188.5 million, 86% higher than the previous year. Furthermore, “VMware delivered its highest year-over-year growth rate in five quarters and the second consecutive quarter of sequential quarterly growth of 20%.”

Additionally, although virtualization can be very helpful in certain areas, not all applications can be virtualized. It will likely take time for IT departments to sort out which servers and processes should be virtualized, as well as selecting which management tools they will use.
“There will be a 3-4 year period of growth as users sort out management capabilities,” predicts Weiss. “There are too many variables to say that this is going to be a mass market anytime soon.”

Finally, the biggest unknown in the market is Microsoft’s latest virtualization product, due for release in 2008. And of course, Microsoft is likely to be a tough competitor.

For all of those reasons, the smart money predicts that the Xen hypervisor will have a major role in enterprise virtualization, but it won’t be knocking out VMWare and Microsoft products anytime soon.