Now that Microsoft has finally embraced the concept of cloud computing with the unveiling of the Windows Azure platform, a new battleground is emerging for the hearts (and wallets) of IT professionals. After ridiculing cloud-based applications like Google Apps, Microsoft has had a change of heart and clambered aboard the cloud computing bandwagon.

Microsoft CEO Steve Ballmer said as much in an email sent earlier this week, saying that "the Azure Services Platform will provide fundamentally new ways to deploy services and capabilities. It gives businesses the option to take advantage of the capacity available in the cloud as it is needed, reducing the need to make large upfront investments in infrastructure simply to be ready when demand spikes. It will enable developers to create applications that run in the cloud and provide the features, information, and interactivity that employees, partners, and customers expect-no matter how many of them there are, where they are in the world, or what device they have at hand."

Microsoft's vision of cloud computing is exactly that: Microsoft's vision. The cloud computing market has a host of players, and VMware (along with Google) represents a threat to Microsoft's dreams of cloudspace dominance. I spoke earlier today with Dan Chu, Vice President, Emerging Products & Markets at VMware, about what VMware sees as the key differences between Microsoft and VMware's competing visions for cloud computing.

"From a customer standpoint \[Windows Azure\] is a very limited offering," says Chu. "It forces a new proprietary architecture on customers, it only works if all of your apps are based on .NET, and you're then dependent on Microsoft as your sole service provider for your mission critical apps." Chu argues that the Windows Azure approach may be difficult for many customers to adopt if they're using Web-based applications derived from the LAMP (Linux, Apache, MySQL, PHP) stack and others apps not based on the .NET framework. (Note: Microsoft did announce at PDC2008 that Windows Azure would eventually support non-Microsoft development platforms, including Java and LAMP applications.)

Chu also contends that Microsoft's annnounced cloud computing strategy is an attempt to control the direction the market is taking, and redirect the discussion back to Microsoft and its products. "It's part of the Microsoft playbook to try and control an emerging market that is evolving away from being centered around a Microsoft family of products," Chu said.

When asked to compare VMware vCloud product roadmap with Microsoft's Windows Azure strategy, Chu highlights three areas that he believes Windows Azure will fall short, including Microsoft's new role as a service provider, incompatibility with existing applications based on LAMP technology, and that Windows Azure is still months -- if not years -- away from being a tangible product.

"With vCloud, we don't become a service provider," says Chu. "Microsoft is stepping over the line, and now intends to compete directly against some of their \[hosting and service provider\] partners." By comparison, Chu argues that vCloud is a platform that is supported by a broad range of third-party service providers, including British Telecom, Saavis, Rackspace, Terremark, and others.

The second failing of Windows Azure Chu sees is the lack of support for applications and platforms that aren't based on the .NET framework. "\[With vCloud\] we're looking to support a broad range of existing applications...without forcing customers to rewrite applications, or to only have certain kinds of apps, "says Chu. "VMware's products are already providing a platform that people are using to deploy internal clouds, and that our partners are already using to create external clouds."

Gartner Analyst Thomas Bittman agrees, writing in his blog that the need for applications to be rewritten or redeveloped to support Windows Azure could be a deal-breaker for some enterprises:

But, Azure doesn’t support existing applications – applications need to be targeted originally for Azure. With Azure, sourcing is not a runtime operations decision, it is an application design decision. The software and/or services decision is kinda hardwired at design time, which is unfortunate, and means that enterprises will need to look elsewhere for solutions to cloudsource some of their computing requirements.

That leads to Chu's final point. According to Chu, VMware's vCloud and VDC-OS will eventually allow customers and service providers to federate across internal and external clouds to make a "seamless IT infrastructure using a common framework", and that a good portion of the technology required for that transition is already in use by VMware customers in the form of ESX Server and VMware Infrastructure 3 (VI3). "From our standpoint, we have proven technology that is already being used for internal clouds...the core \[technology platform\] is already there."

Chu also stressed that while Windows Azure was announced this week, hundreds of thousands of VMware customers are already using VMware products today. "The Microsoft cloud is not real today," says Chu." "It doesn't exist yet."

In fairness, the vCloud aspect of VMware's cloud strategy is almost as ephemeral as Microsoft's is. And in a prime example of dueling analyst perspectives, Gartner's David Smith told CNET News.com that the unveiling of Windows Azure was "very ambitious, extremely ambitious," and that Microsoft's cloud computing approach was a "very visionary, pragmatic idea."

VMware does have a sizable market share and product development advantage on the virtualization front, and hopes to leverage their leadership position there -- in conjunction with VDC-OS and vCloud -- to keep one step ahead of Microsoft. Time will tell which vision of cloud computing will emerge as the dominant one, but the industry is clearly experiencing the opening skirmishes in a long and protracted battle over the future of business IT.