Will Linux take the lead in server virtualization?

For server vendors such as Dell, Linux is a good thing because it lowers acquisition costs for customers. It's easier for a customer to commit to deploying a new server when software license fees are removed from the equation.

You might assume, then, that virtualization is a bad thing for server vendors. A customer might be less likely to buy new hardware when the alternative is to load up VMware with an additional, virtual instance of the OS and applications.

But that's not necessarily so, says Paul Gottsegen, vice president of worldwide enterprise marketing at Dell. At a meeting at Dell's Round Rock, Texas, headquarters last week, Gottsegen explained that the advantage of virtualization is that it drives up utilization on individual machines, thus increasing the total return on those investments. Continued high utilization makes it easier for CTOs to justify past expenditures and to make the case for increased technology investment in the future.

For customers, the combination of open source and server virtualization is a double win. This combo makes it possible to deploy a server at the minimum possible cost while enabling the maximum possible utilization for that resource over the long term. Little wonder that Linux vendors, including Novell and Red Hat, are looking to virtualization to provide the next big push for the open source OS.

Central to their plans is Xen,  an emerging, open source virtualization environment for x86 processors. Similar to VMware, Xen allows administrators to securely run several virtual machines on a single physical system with performance comparable to native code.

"We just saw a demo of 50 virtual machines running under Xen," Marco Pena of Dell's enterprise product group told me. "It was amazing."

The most significant difference between Xen and VMware, ironically, is that Xen actually tries to do less and in so doing delivers more. VMware, as do most other virtualization environments, abstracts the entire x86 hardware environment. That makes it very flexible; practically any operating system can run in a VMware virtual machine. The downside is that it has to expend a significant number of processor cycles, making sure that none of those various systems interferes with the others.

Xen avoids this problem with a simple solution: The operating system has to "know" it's running under Xen. Of course, that's difficult to do with Windows -- and in fact, Windows won't run under Xen today -- but in the open source world, there's nothing stopping developers from modifying the OS kernel for Xen support.

Despite this under-the-hood approach, however, Xen is far from a mere hobbyist solution. A range of companies, including AMD, HP, Intel, Network Appliance, and Veritas, have contributed significantly to the project. Leading the charge is XenSource, a company that manages the open source effort while simultaneously marketing enterprise products based on Xen.

No one is more excited than the Linux vendors, however. When I met with Red Hat's new CTO Brian Stevens in early December, he told me in no uncertain terms that a large portion of his company's development resources are going toward perfecting the upcoming version of Xen.

"RHEL [Red Hat Enterprise Linux] 5 is ready when Xen is ready," Stevens said.

More and more people are turning to virtualization as the solution for managing their complex datacenters. Given the backing behind Xen, Linux appears poised to become the premiere virtualization platform. It will be interesting to see what transpires after Microsoft does the math.