Microsoft vs VMware: the hypervisor wars

End-users stand to lose from competitive approach, says Robert L Mitchell

As Microsoft readies Hyper-V, the new hypervisor software that forms the foundation for virtualisation in Windows Server 2008, VMware is finally facing some real competition in the Windows server virtualisation market. Unfortunately, Microsoft has followed in VMware's footsteps by creating its own, proprietary way of doing things, and VMware doesn't want to play along. The result: IT departments face a choice between two virtualisation options that are incompatible.

Virtualisation services are built on top of a thin layer of code, called a hypervisor, that sits on top of the hardware and abstracts it away from the virtual Windows servers running above. The primary purpose of this program is the redirection of requests between multiple virtual machines and the underlying hardware so that each VM thinks that it is in charge. It is, in essence, basic plumbing.

The idea that the hypervisor would evolve to become a commoditised, standardised substrate, and that innovation would occur in the software layers above that, isn't happening. Instead, this contest is shaping up to be more about a clash of the titans, where two companies with near-monopolies in their respective markets pit one proprietary design against another. You want in? Write to our APIs.

Microsoft, which owns the operating system, has already released a beta of Hyper-V and the final release is expected in the next few months. VMware, which dominates the Windows server virtualisation market with its ESX offering, continues to hone its own tools within the VirtualCenter suite. Over the next year, users will have a choice between two virtualisation management stacks that can't interoperate because each has innovated at the plumbing level.

And that's just fine by VMware. "We have never believed that the hypervisor would be commoditised," says says Ben Matheson, director of marketing at VMware. "To imply that it's a commodity would imply that there's no differentiation," he says.

What VMware and Microsoft are battling over is a tiny bit of code (Hyper-V is just 800KB in size) that is sandwiched inside the industry-standard WinTel platform, between the x86-standard iron and the de facto standard Windows operating system.

With the imminent release of Hyper-V, Microsoft's first true hardware-level virtualisation offering, the goliath of Redmond may think it's clobbering time for VMware. However, it's about three years late to the party.

Vendor efforts to continue to differentiate at the hypervisor layer are reminiscent of where networking was more than 30 years ago, when everyone thought they could do networking better. Gradually, the market came to accept the idea that by moving to a standard substrate (TCP/IP over Ethernet) and innovating higher up the software stack, they could get a piece of a much bigger pie. With virtualisation, vendors aren't yet ready to see the bigger picture. Today, it's still about speeds and feeds. Says Matheson: "We can support more virtual machines than Microsoft's [hypervisor] can."

If all server-based computing is in the early stages of a mass migration onto virtual machines, the lack of a standard hypervisor for Windows will only serve to retard that transition. That vendors feel compelled to compete at this level shows just how nascent virtualisation technology is, despite the fact that many enterprises now depend on it. The appearance of an incompatible Microsoft hypervisor is also leading to a sense of caution. After all, many IT departments have already heavily invested in VMware products.

Hotel operator MGM Mirage has standardised on VMware but is otherwise a Microsoft shop. "VMware doesn't work on all of these [Microsoft] products today," says CIO Tom Peck. VMware can get away with that because it was first to market and has a more mature management framework for the enterprise, he says, but he's not happy about the idea that his VMware management suite won't work with Hyper-V.

The virtualisation battle between Microsoft and VMware leaves Peck and other CIOs feeling a bit stuck. On the one hand, they want to leverage Hyper-V, a lean software layer that has been performance-optimised for Windows. But doing so means abandoning VMware's Virtual Center and associated management tools such as VMotion and Distributed Resource Scheduler. Microsoft's virtualisation management offerings are nowhere near as advanced, and VMware has no intention of making its tools compatible with Hyper-V. "There's not much value in doing it," says Matheson.

To fight the proprietary performance advantage that comes from Hyper-V's tight integration with Windows Server 2008, VMware has rolled out ESXi, a slimmed-down (32MB) version of the ESX hypervisor that some server vendors are embedding into server hardware on an internal USB flash drive. VMware won't say what it charges server vendors for ESXi, but in the grand scheme of things, the incremental cost to server buyers is likely to be negligible. Microsoft is selling Hyper-V for US$28 and would probably give it away for free if the company could get away with it.

Why US$28 and not zero dollars? "It does get weird and wonky when [Microsoft] gives things away," says Windows Server 2008 product manager Ward Ralston. "We can't do that because of who we are," he says, given previous run-ins with regulators over Microsoft's alleged monopolistic practices in the past. Regardless, both vendors are essentially giving away the hypervisor to capture the business — and lock in the customer. Today, VMware has the advantage in that it has already locked in many customers with its VirtualCenter offering, which is tightly coupled to its own hypervisor.

Microsoft wants to own the hypervisor by embedding it into Windows in much the same way it has extended Windows in other areas, pushing aside major competitors. VMware is well aware that if it supports Hyper-V, it risks losing control over its own destiny. But this competitive battle doesn't serve the needs of IT managers, who want a common hypervisor that allows them to use the management tool stack of their choice.

Will a more open, standardised hypervisor layer evolve for the Windows server market, or will this turn into a Blu-ray vs HD DVD battle, in which one proprietary hypervisor wins? MGM Mirage's Peck thinks customers will demand openness. "The winner of this race is going to be the product that can be more open and more interoperable upstream, downstream, left and right," he says. VMware may think it's ahead. But, he adds, "right now, neither one of them is winning in that space".

Vendors have yet to reach that conclusion, however, and that consensus, if it ever comes, is likely to take a few more years. In the meantime, Microsoft and VMware seem determined to slug it out for dominance. Let the hypervisor wars begin.

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