Mix-and-match trouble with virtualization, cloud computing

easy to imagine how you can move from one [vendor's product] to another," Rosenblum says. "At a higher level, I assume if I can get all my data into Salesforce and use it, then taking it to some other CRM provider would be relatively easy as well."

All those points are among the benefits that make cloud computing attractive as a generic idea. Buy what you need when you need it without having to worry too much about formats or operating systems or other vendor lock-in issues.

"Ultimately what you want to own is an application," Vogels says. "You don't want to own a machine or an operating system. At the end of the day you want to have the data and the application and don't want to have to worry about standardization."

In a cloud-computing model the operating system, "this thing that was really crucial to bind the interface to the hardware," Rosenblum says, "it will be there, but it will be part of the applications. You'll just pick from this set of applications and what you pick will come with some piece of the operating system in a package that you'll need."

Which is nice, but leaves the question of what kind of virtual infrastructure to buy completely unanswered. Amazon built its system on Xen because it was open-source, relatively inexpensive and Amazon had the expertise in-house to handle code that's wonky even for an infrastructure product.

The cloud computing world is not going to standardize on Xen, though, or ESX or Hyper-V or any other specific product, panel members agreed. Interoperability and vendor independence isn't just part of the cloud-computing ethos, it's one of the technical requirements.

Virtualization-and the hypervisors, operating systems, VM-management software and all the other components of virtual infrastructures from Microsoft and VMware-becomes only one piece of a cloud-computing model, and not that critical a piece.

Virtualization, according to Rosenblum, who is as responsible as any single person can be for the availability of virtualization in a form that's practical for corporate IT, is a logical step on the evolution toward network-based cloud computing model.

Think about that the next time you have a conversation over whether VMware or Microsoft is a better short-term, long-term or any-term virtualization provider, or whether you're getting fleeced by choosing the one you've already chosen.

Virtualization, as much as cloud computing, is inherently a vendor-independent function, no matter how inadequate or purposely inconvenient the interoperability of specific products currently is.

To work right and deliver on its full potential, virtualization vendors have to give customers the freedom to choose the operating systems, management tools and other products that work most effectively for them.

That, typically, doesn't translate into a single-vendor solution, no matter how much either VMware or Microsoft pushes for it.

Not doing so makes the possibility of adding or expanding IT into the cloud more difficult and that, more and more obviously, is the kind of holdup corporate IT managers just will not be able to abide.