Data backup, archiving and disaster recovery are three likely uses for the cloud, says Engate.

"The cloud is for any kind of large-scale storage need with any kind of static-type data," he says. "You don't want to store a database in the cloud, but you might store a historic copy of your database in the cloud instead of storing it on very expensive SAN or NAS technology."

"A good rule of thumb is to consider cloud storage only for latency-tolerant applications," says Terri McClure, a storage analyst at Enterprise Strategy Group in Milford, Mass. "Backup, archive and bulk file data would all do well in the cloud, where subsecond response time is not a requirement." On the other hand, databases and any other data that is "performance-sensitive" aren't suited for cloud storage because of latency, she notes.

But before moving any data to a cloud, public or private, users need to address a more fundamental question, says Mark Tonsetic, program manager at The Corporate Executive Board's Infrastructure Executive Council.

"If you go to cloud storage, does it solve the problem of understanding where and why storage growth is out of control and where the point of value is [in storing a particular set of data] in the entire end-to-end business process? Just moving the technology to a cloud is not an optimal solution," Tonsetic says.