Xen lets multiple operating systems run on the same computer, a feature that's useful for extracting as much work as possible from a single system. The technology is common among high-end servers today, but on mainstream systems it requires proprietary "virtual machine" software from EMC subsidiary VMware.
At the LinuxWorld Conference and Expo here, numerous companies voiced Xen support in the form of endorsements, programming help and software contributions. Sun Microsystems, Hewlett-Packard, Novell, Red Hat, Intel, Advanced Micro Devices and Voltaire all are involved, but one of the more interesting allies is IBM, which has decades of experience in the area.
"Two or three months ago, it wasn't on anybody's radar. Now it's going to make a big change in how everyone uses Linux," said Chris Schlaeger, vice president of research and development for Novell's SuSE Linux.
The change illustrates what can go right in the world of open-source software: a project can trigger a cascade of cooperation by multiple interested parties. When it works well, as in the case of Linux, that cooperation can lead to a unified, fast-developing project rather than proprietary, mutually incompatible competitors.
"The open-source community has finally decided to smooth over its differences and get behind one virtualization project, which means it's actually going to happen rather than having 12 warring fiefdoms, each with about two soldiers," said Illuminata analyst Gordon Haff.
Xen began three years ago at the University of Cambridge in England, said Ian Pratt, project leader and a founder of XenSource, a start-up that develops and supports the software and is trying to make it a standard computer feature. "Being ubiquitous on Linux is the first step to that," he said.
Xen and other approaches to dividing a computer into separate partitions rely on a concept called virtualization, which lets programs run on a software simulation of actual hardware. In the case of VMware, this foundation is called a virtual machine.
One difference between VMware and Xen: The former completely simulates a machine, which theoretically allows any operating system to run unmodified on a virtual machine. Xen, on the other hand, uses "paravirtualization," which doesn't go as far. That means faster performance but also requires an operating system to be modified to run, Pratt said.
Higher-level software, however, doesn't need to be modified, he said.
The requirement for a modified operating system will loosen with Intel's coming Vanderpool Technology, or VT, due in 2005, Pratt said. It will mean unmodified operating systems will run on Xen, though not as fast as modified ones. That means Windows will run on Xen even though open-source programmers don't have access to change Windows itself.
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