IDG News Service — Skeptics who disparage the concept of the so-called private cloud and doubt its relevance should think again, according to research from IDC.

In a recent survey, IDC asked IT executives about their preference for using a private versus a public cloud. Fifty-five percent said that a private cloud was more appealing than a public cloud, and 22 percent said they were equally appealing, said Frank Gens, an IDC chief analyst who spoke on Thursday at an IDC Tech Outlook event in Seattle.

There are varying definitions for a private cloud, and some people say it's just a new term to describe IT integration efforts that have been in the works for years, he said.

IDC defines a private cloud as an internal corporate cloud resource where the IT organization is the vendor, offering self-service provisioning, pay-per-use options and simple access, potentially through a browser.

The concept emerged over the past few years as IT departments continued to struggle to build integrated, efficient and quickly deployed IT systems. They began to notice that some of the public cloud vendors had achieved the same goals by building new data centers from scratch. "They said, why not make the job of the CIO easier by borrowing tricks from the public cloud?" Gens said.

IDC's research shows that many companies expect to use both public and private cloud services, with a preference for private clouds. When asked about where they would run specific services, 75 percent of respondents said that they'd run collaboration applications on a private cloud and 53 percent said they'd run e-mail on a private cloud.

"There's clearly a higher comfort level with private versus public," Gens said.

Still, he believes many companies will use both kinds of clouds. "If you scoff at the idea of a private cloud, you're in peril," he said. "But public clouds will drive a lot of solutions, so don't be too cocky if you're a private-cloud evangelist. Virtually every customer, at least from the midmarket up, will have a mix of both."

Some individual applications may use both kinds of clouds. For example, the cache might reside in one and the operations in another, he said.

IDC is expecting significant growth in public cloud services over the next few years. Revenue from IT cloud services exceeded US$16 billion in 2009 and should reach $55.5 billion in 2014, the research group said.

IDC is a division of International Data Group, the parent company of IDG News Service.