Tech Industry

Xen passes Windows milestone

XenSource says it has succeed in booting Microsoft's OS on the Xen virtual machine software, aided by an upcoming Intel chip.

SAN FRANCISCO--Start-up XenSource has succeeded in booting Microsoft Windows on top of Xen software, an important milestone in its effort to commercialize the virtual machine.

XenSource said Tuesday it accomplished the feat using an Intel processor equipped with VT, or virtualization technology--a feature scheduled to begin shipping in new chips later this year. The Palo Alto, Calif.-based company is demonstrating the software this week at the Intel Developer Forum here.

Xen, which is designed to let multiple operating systems run on the same computer, is almost always is used with Linux. But running Windows as well is useful in the real world, where both operating systems are widely used atop the powerful networked computers called servers.

Beginning later this year, XenSource plans to sell management software called XenOptimizer to help customers use Xen.

Getting Windows started on Xen wasn't easy, said Simon Crosby, a XenSource co-founder and vice president of corporate development for the 45-person company. For example, the boot process uses 16-bit code from that must be emulated on today's 32-bit and 64-bit chips, he said.

The XenSource programmers booted Windows XP SP2, Crosby said.

Xen software is a "hypervisor"--software that manages a computer's hardware resources so they can be shared by multiple operating systems. By virtualizing and sharing this hardware, computers ideally can juggle more jobs gracefully and efficiently.

Xen uses an approach called "paravirtualization," in which the operating system must be modified to be aware of the hypervisor layer. Future versions of the two most commercially successful versions of Linux, Red Hat Enterprise Linux and Novell's Suse Linux Enterprise Server, will include the necessary modifications.

With the VT features of Intel's chip, though, an operating system can run on Xen without having to be modified. The chipmaker's engineers contributed the initial Xen support for VT, Crosby said.

Intel's chief rival, Advanced Micro Devices, has a parallel technology called Pacifica that it plans to introduce in 2006. Though Pacifica and VT work somewhat differently, Xen employs a software layer called VMX that is designed to handle differences chip technologies.

Xen engineers will be able to start building Pacifica support soon, Crosby said. "We're expecting evaluation systems shortly," he said.