April 04, 2006

Free MVS, Xen, and Intel

Today's interesting tech news is that Microsoft is giving away - free as in beer - the Microsoft Virtual Server 2005 product. The reason this giveaway is grabbing headlines is that MVS 2005 can host Linux - free as in speech - on top of Windows. This will make it easier for Windows shops to try their hand at hosting tons of Linux servers (although without abandoning Windows). Welcoming the neighbors in (for free) is an unexpected move by Microsoft!

So the news lead me to read some more about recent goings-on in the world of virtualization. What I found was interesting...

It turns out that long-time virtualization leader VMWare is considered to be under siege, not by Microsoft, but by a GPL'ed high-performance alternative called Xen.

Xen originated as a research project lead by Ian Pratt and other Cambridge researchers (including Paul Barham from Microsoft and Rolf Neugebauer from Intel). The basic idea behind Xen (paper) is slightly different from VMWare. Whereas VMWare sandboxes the entire hosted operating system to virtualize every privileged instruction (recompiling dynamically), Xen instead requires the hosted operating system to be rewritten to avoid privleged instructions in the first place. On current Intel architectures, the OS modifications are necessary in order to run the hosted OS at a lower privilege level than Xen.

It turns out that the cooperative virtualization approach results in much higher performance than VMWare. And the OS modifications are practical - Xen can host 2.4 and 2.6 flavors of Linux, and NetBSD, FreeBSD, and Plan 9 ports are in the works. Amazingly, in a previous life, there was a verion of Xen that ran a modified Windows XP (but which, unamazingly, the license prohibits them from distributing).

So Xen is has lit up the runway to free, high performance virtualization between all operating systems. Could we soon find ourselves in a world where operating systems no longer matter, where an OS is just another app? Perhaps. Although it doesn't really make a big difference if Microsoft Windows is not one of those operating systems. If you can't host Windows in Xen, then the world hasn't changed all that much, other than lowering the cost structure of some service providers and throwing VMWare's business model into disarray.

But then a note in this article caught my eye: Intel will soon be introducing Vanderpool modifications to the x86 architecture to improve hardware support of virtualization (and which will compete with AMD's Pacifica virtualization). The expected upshot? Any operating system can be virtualized in a cooperative Xen-like way without modification, and Microsoft Windows will be able to be virtualized inside Xen - free as in speech - and as an equal peer to Linux - without Microsoft's help.

In the epic platform wars, "who's on top" is the only question that matters, and for years the OS has been the alpha-male king of the hill, "Intel Inside" notwithstanding. I have never really thought of Intel and Microsoft as adversaries, since they depend on each other so dearly. But virtualization puts the chip on top instead. And so when you think about things in a Xen way, perhaps all this virtualization maneuvering is really a spat between the two 800-pound gorillas of the tech world.

Is free MVS really a shot by Microsoft to try to get in front of Xen and block the rise of Intel to king-of-the-hill? I don't know.

But either way, it might be nice to have a "Linux/Windows/Mac" gearshifter on my Intel box.

Posted by David at April 4, 2006 11:17 PM

Good summary. I know of a large software house who provide test servers to their devs out of Xen clusters. A couple of years ago they were using VMWare for this.

The thing about the hardware support for virtualization is totally about Windows - most new Linux distros come with Xen support anyway. There were rumors that Apple was going to replace Mach with a Xen-based kernel (especially now that Avie has left Apple).

Finally, don't forget http://www.parallels.com/ who are releasing a hypervisor for the Mac later this week.

Posted by: RichB at April 5, 2006 02:40 AM
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