On Sunday EMC vice president and global marketing CTO Chuck Hollis wrote in his blog about the merits of private clouds.

The emergence of private clouds - which work in the same way as public cloud services, but are run by the enterprises themselves - will play an important part in this evolution of IT systems, according to Hollis. They have all the advantages of public cloud computing for enterprise IT without the downside, because IT departments retain control of security and legacy applications won't have to be rewritten, Hollis said.

"One of the more powerful ideas behind private clouds is the notion that you can own all, some or none of your IT infrastructure. More importantly, the mix of resources can potentially change moment-to-moment," Hollis wrote.

On Monday Cisco's chief technology officer Padmasree Warrior addressed reports of an impending datacentre push in a Cisco blog. Warrior doesn't use the term "cloud computing" when describing Cisco's vision of "Unified Computing", but "building a next generation datacentre that links all resources together in a common architecture" isn't far off being just that.

Both Hollis and Warrior wrote of the potential new architectures, virtualisation and automation hold for improving the effectiveness of IT systems.

However, while they hold out the benefits of a private cloud, they will also use this as an opportunity to lock customers into their own solutions, according to Andrew Butler, vice president at research firm Gartner. The message is that only by tying yourself to one vendor will you achieve the full benefits of a private cloud, he said.

"What you've got are these big system vendors who are increasingly reluctant to share the spoils," he said.

EMC (with VMware in tow), Cisco and a number of other vendors aim to position themselves as the vendor of choice for building next generation datacentre services, with the intent of grabbing a larger part datacentre budgets, according to Butler.

So far the nascent private cloud arena has been dominated by smaller companies, including Elastra, 3Tera, Cassatt and ParaScale. But the concept of private clouds is gaining prominence, according to Butler.

Just recently Sun acquired Q-layer. Its NephOS will allow enterprises to create and manage their own private computing clouds by linking facilities operated by different divisions of the enterprise.

ParaScale, which develops software for cloud storage clusters, has seen increased interest in private clouds.

Now, especially the larger companies are thinking that they can leverage their scale to provide cloud services to internal customers, instead of placing data and applications in the hands of external parties, said CEO Sajai Krishnan via email.

Both Warrior and Hollis are vague about upcoming products. EMC has, for example, already got Atmos, a storage product targeted at newer storage clouds, but there is more to the story, said Hollis via email without elaborating.

Warrior didn't go into any detail on upcoming datacentre products, except to say that Cisco is developing them.

Butler believes Cisco's push into the server space makes sense. "When you get to Cisco's level of domination, unless there is significant organic growth in the market, it becomes difficult to sustain success, and you have to start looking elsewhere. I think what we have here is a recognition on Cisco's part that it has to influence decision making at a higher order in the datacentre," said Butler.