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Guest operating system support and Microsoft's conflict of interest

Limited guest operating system support highlights Microsoft's tricky balancing act: functioning as an operating system vendor and a virtualization vendor.

As the creator of both the Windows operating system and the Hyper-V hypervisor, Microsoft has a conflict of interest.

Virtualization provides value at several layers of data center operations. The deeper that a hypervisor can go into your data center, the more valuable it is. Conversely, the less guest operating system support there is, the fewer benefits the hypervisor can provide. Many IT groups have moved toward a 100% virtualized data center, but limiting guest operating system support -- as Microsoft does -- can stop these efforts in their tracks.

For more on guest operating system support
Guest virtual machine and host server definitions

What is a guest OS?
Comparing guest operating system support
Let's take a look at the guest operating systems that Hyper-V supports compared with those supported by VMware. Granted, this list is generated by VMware, but it is a good side-by-side comparison, and it matches up to Microsoft's own operating system support list.

Note that VMware's guest operating system support for Windows NT 4, Windows 98, Windows 95, Windows 3.1 and DOS 6.22. These are Microsoft OSes, but none are supported in Hyper-V. In fact, I would venture to say that they are not supported in Hyper-V is because they are Microsoft OSes. That doesn't sound right, does it? Well, keep reading.

Two interesting blog posts --"Hello Hyper-V : Meet Reality," and "Hello Hyper-V : Meet Reality (part deux)" -- touched on guest operating system support. In the first post, Ben Armstrong, virtualization program manager at Microsoft, added the following comment:

What we often talk about on the Hyper-V team is "Support versus support". Hyper-V can run Windows NT 4.0 -- and I would love it if we said that we support it, but we cannot say that -- because Microsoft as a whole does not support Windows NT 4.0. And it really changes the story when you are the OS maker.

That last sentence resonates with me. It does change the story when you are the OS maker. And it runs in direct contrast to what the goals of a hypervisor vendor should be. To me, that statement read, "To promote a unified support model between the many applications, OSes and marketing teams within Microsoft, we are imposing artificial limitations on Hyper-V support."

We have seen Microsoft impose such limits this before, as it did in adjusting its virtualization licensing to limit the advanced VMware features that Microsoft's own virtualization products could not support. As soon as Hyper-V could support these features, Microsoft made its licensing models more friendly. Windows has been restricted to promote Hyper-V, and now Hyper-V has been restricted to promote newer Microsoft OSes.

Guest operating system support for legacy apps
Do not fool yourself into thinking that the OSes in question are antiquated products that no one cares about. There are still a good many legacy systems that serve as critical pieces of businesses' infrastructure. NT 4 is most prevalent, but I have virtualized environments running Windows 98 and DOS 6.22 on VMware. In these cases, it was difficult to find modern hardware that could run these legacy applications, and virtualizing such applications on VMware extended their life.

Did VMware provide support for DOS as an OS? No. But by supporting DOS as a guest operating system on its hypervisor, VMware provided us with the necessary physical-to-virtual migration tools, support and documentation to virtualize these workloads.

That is where Microsoft's conflict of interest is obvious. From a hypervisor vendor, I look for support in virtualizing workloads. From an OS vendor, I look for support in maintaining the OS. When the two begin working behind the scenes, each limiting their own support in an attempt to assist the other, who wins? Certainly not end users.

About the author
Mark Vaughn (MBA, VCP, BEA-CA) serves as an enterprise architect for a multinational corporation. Vaughn has more than 14 years of experience in IT as a Unix administrator, developer, Web hosting administrator, IT manager and enterprise architect. For several years, he has focused on using the benefits of virtualization to consolidate data centers, reduce total cost of ownership, and implement policies for high availability and disaster recovery. Vaughn is a recipient of the 2009 vExpert award and has delivered several presentations at VMworld and BEAWorld conferences in the U.S. and Europe. Read his blog at

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