VMware has put some flesh onto the bones of its plans for cloud computing at the VMworld Europe 2009 conference in Cannes this week.

The company's vision includes the ability for VMware customers to turn their datacentres into internal clouds focused on delivering services as required, and to enable them to buy extra capacity from cloud service providers whenever necessary.

Dan Chu, vice president of emerging products at VMware, has overall responsibility for the company's vCloud initiative. He explained that, after listening to customers, the company is not only enabling the enterprise cloud, but delivering what it terms the "private cloud" formed from the combination of a customer's own resources and that of any third-party cloud it is utilising.

"We heard from customers that choice is key, and that they want the ability to run with already trusted service providers such as BT or Savvis or Terremark, but that they wanted the ability to be able to switch provider if necessary," he said.

Businesses also want to be able to move application workloads seamlessly between internal and external clouds. According to Chu, some VMware customers are already doing this in a rudimentary fashion, using external services to test and develop applications, then moving them back internally once the testing phase is over.

But to realise the vision of a broader market for cloud-based services, there need to be standards for interoperability, something that does not currently exist to any major degree.

"Standards are important. We see standards in terms of how applications and virtual machines are packaged to run across clouds, but also in how clouds are managed," said Chu.

Without such standards, cloud services are in danger of becoming dominated by a handful of proprietary "mega clouds" operated by companies such as Microsoft or Google, according to Chu, which will lock customers in and other vendors out.

He contrasted this with VMware's strategy, which he claimed is to be an enabler rather than an operator of cloud infrastructures.

On the packaging front, Chu said that VMware had been instrumental in driving the Open Virtualisation Format, a specification for packaging virtual machines that is not tied to any specific hypervisor or processor.