VMware, Xen clash over patch

Things don't always go smoothly when you try to mix the world of open source with the world of proprietary commercial software. Sometimes those worlds collide.

Case in point: the current hubbub over virtualisation support in the Linux kernel. Virtual servers are all the rage, and the current technology darling in the Linux world is a project called Xen, an open source hypervisor that lets you run multiple instances of Linux on a single machine.

Support for Xen is a much-touted feature of Novell's new SUSE Linux Enterprise Server 10. But not every vendor is so bullish.

According to an executive at Novell rival Red Hat, Xen is "not ready for the enterprise" -- so don't expect to see it in Red Hat Enterprise Linux anytime soon.

Meanwhile, Xen's efforts to further integrate into the Linux kernel have run into opposition from a predictable source: proprietary virtualisation software leader VMware.

It seems VMware has been working on a hypervisor-based virtualisation technology, similar to Xen's, for an upcoming release of its commercial virtualisation product line. Like Xen, VMware's technology will work better on Linux if the Linux kernel gives it a little help and so, like Xen, VMware has been submitting long lists of patches to the kernel developers for review and possible inclusion in the kernel.

And wouldn't you know it, the Xen group's patches and VMware's patches are totally incompatible with each other.

Both approaches will work: both groups have an established history with Linux kernel development. And so, only naturally, the kernel developers prefer not to take sides. They're not going to accept either set of patches until VMware and Xen hash out their differences and come to a compromise -- something that, so far, neither seems willing to do.

All this squabbling is bad for business, of course, especially for vendors such as Red Hat that are waiting for Xen to mature before they green-light it for enterprise use. In fact, Oracle is "losing patience" with the situation, according to one executive, and may start putting pressure on the various players to step up negotiations.

Isn't that always the way? Perfectly good open-source projects are minding their own business, when all of a sudden a proprietary software vendor such as VMware comes along and spoils it for everybody. Then even bigger proprietary companies step in and start pushing everyone around, and the whole thing's a mess.

But hold on. Not everything is as it seems here.

As it turns out, VMware's proposal to the Linux kernel developers is not proprietary software at all. It's a fully open standard called Virtual Machine Interface that provides a generic interface that can support multiple forms of hypervisor-based virtualisation -- including, potentially, Xen.

The Xen developers' proposal, on the other hand, is 100 percent specific to Xen -- so much so that it's completely unsuitable for VMware's needs (or those of anyone else who might come along). Xen could do things VMware's way, but its developers prefer not to. Period.

Ironic, isn't it? Xen is open source, but it is VMware's proposal that best matches the spirit of open source software. Meanwhile, XenSource, a key sponsor of the Xen project, has been busy inking a deal with Microsoft to run Xen on Windows, even as it resists negotiations over its Linux kernel interface.

It just goes to show, there's more to open source than source code.

The spirit of participation and collaboration is what lends open-source its strength, and what makes it a win for customers. Commercial software vendors can have that spirit, too; and just because your code is open doesn't automatically make you the good guy.