In the emerging cloud computing market, a new term--private clouds--is creeping into the lexicon. It refers to corporate data centers adopting the technologies and practices of public cloud infrastructures such as those Amazon.com and Google operate. This best-of-both-worlds model just got another push forward.

Elastra, a startup that has developed a "cloud server," last week disclosed it received $12 million in second-round funding from, among others, Amazon. Elastra's technology--including two markup languages for describing the components of cloud applications and how the applications are to be deployed--is used by about 40 customers to manage applications in Amazon's Elastic Compute Cloud and Simple Storage Service (S3).

Elastra's next milestone (due in October) is a VMware-tuned version of its server that can be used for cloud-like application management inside a company's firewall. "That's the private cloud in your data center," says CEO Kirill Sheynkman. When that's available, he says, Elastra's tools can be used to design applications once that run in both public and private clouds.

Why the interest in private clouds? IT departments have long sought utility-like IT environments where computing resources and applications can be provisioned with greater efficiency. They're using systems management software, cluster and grid technology, load balancing, and virtualization to do it. Technologies like Elastra's Cloud Server are the next step. Other private cloud products include 3Tera's grid operating system, ParaScale's disk-storage aggregation software, and Cassatt's resource-pooling technology.

The drawback of private clouds is that IT departments still have to buy, build, and manage them. The original premise of cloud computing--think Salesforce.com--included lower up-front capital costs and less hands-on management by IT staffers.

That said, private clouds are driven as much by what CIOs don't like about public clouds. Concerns about data security, corporate governance, and reliability dog cloud service providers. Amazon's S3 service was down for eight hours on July 20. Private clouds theoretically can deliver some benefits of cloud computing without the pitfalls.

HAZY FORECAST

For now, few businesses have plugged into public cloud services and even fewer have created private clouds. Russ Daniels, Hewlett-Packard's CTO of cloud services strategy, says we're still in early-stage adoption for both. "A hybrid environment will be typical for most enterprises," he says.

Among the cloud computing research under way at HP Labs is the scalable storage project, which has a goal of designing a self-managing storage appliance with petabytes of capacity for use inside corporate data centers. Apparently, despite its "everything as a service" marketing slogan, HP is planning long term for private clouds.

No surprise, then, that experts are struggling to describe this class of software, storage, and computing services, some of which are delivered over the Internet and others from within companies. "Perhaps you should reconsider your terminology. Cloud is an architecture, not a service," writes Mike Maxey, ParaScale's director of product management, on InformationWeek's Cloud Computing blog.

Cloud computing needs new lingo? Uh-oh, here we go again.