That was the prediction Monday from Patrick Harr, founder and CEO of online storage vendor , one of several speakers at to address the emerging cloud storage market.

"You will see a spending shift from what I call the traditional box model to more of an on-demand service model going forward," Harr told attendees at the conference in Dallas. (, OnStor and FalconStor are among at Storage Networking World.)

When Harr began raising money for Nirvanix, the notion of the "cloud" was barely talked about, he said. Nirvanix didn't even mention the word "cloud" when it came out of stealth mode with a in September 2007. Although Nirvanix now uses the word to market its online storage service, Harr said the buzzword's ubiquity makes it difficult to cut through the hype and figure out exactly what cloud storage is and is not.

Cloud storage is not suitable for all data types, he noted, because it introduces some latency. "Every data has a storage type," Harr said. "Cloud storage is not meant to replace [storage-area network] storage." (Compare .)

Simply making storage available over the Web does not make it a cloud service, he said. The analyst firm Gartner has defined cloud computing as "a style of computing where massively scalable IT-related capabilities are provided 'as a service' using Internet technologies to multiple external customers."