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Computerworld - Cloud storage may be creating a stir these days, but big enterprise users aren't buying in -- at least not yet.

Meanwhile, vendors are in what one provider calls "education mode," explaining to CIOs, IT managers and other IT buyers that they can save a lot of money by floating their data in public and private clouds.

The one thing both groups seem to agree on is that cloud storage will eventually take off. After all, it's technically feasible, it's cheaper than traditional data storage, and it's becoming more and more secure.

"I look at cloud adoption a little like I look at Linux adoption 10 years ago," says John Engates, chief technology officer at San Antonio-based Rackspace Hosting Inc. "Adoption didn't happen overnight. It came in the back door. The system administrator or developer who did work on the weekend brought in the Linux application he built and showed it around on Monday like a science project. It took a while for people to realize it's a viable way to do things."

Cloud storage is a lot further along than a science project. But is it right for part, or even all, of your organization's data? Here are answers to five key questions that will help you decide whether you should head for the cloud.

1. What is cloud storage, and how does it work?

Ask a dozen people and you'll get a dozen different definitions. In a nutshell, cloud storage is a utility-type service that provides multiple users or "tenants" access to a shared pool of storage capacity, which is accessed over an Internet connection. Storage clouds are scalable, and they can easily expand or contract according to customer needs.

2. What's the difference between a public cloud and a private cloud?

The public cloud is a pay-per-use storage utility. All components sit outside of the customer's firewall in a shared infrastructure that is logically partitioned, multitenant and accessed over a secure Internet connection.

Public cloud storage providers, such as Amazon.com Inc. with its Simple Storage Service, typically charge a monthly usage fee per gigabyte of storage plus an additional bandwidth fee for transferring data to and from the cloud. Public cloud customers require no physical storage hardware or any special in-house technical expertise.

Rather, the cloud storage service provider manages the storage infrastructure, pooling its capacity to accommodate the needs of multiple customers. Users typically access their publicly stored data via an Internet connection.

A private storage cloud is usually built behind a company's firewall, using hardware and software owned or licensed by the company. All of a company's data remains in-house and is fully controlled by in-house IT staffers. Those staffers can pool storage capacity to be shared across different departments or used by different project teams within the company, regardless of their physical locations.

As with public clouds, storage capacity can quickly and easily be increased by adding servers to the pool. ParaScale Inc.'s Cloud Storage product and Caringo Inc.'s CAStor are two examples of applications that can be used to set up private cloud storage systems.