IT hosting vendor Rackspace is launching a cloud storage offering, providing storage over the Internet similar to Amazon's S3 service.

Rackspace specializes in providing IT infrastructure as a service, giving customers access to servers and storage located at eight Rackspace data centers worldwide. With CloudFS, an offering in beta mode from Rackspace's Mosso division, the vendor is bolstering its portfolio with a storage option that can be accessed on-demand and scaled to greater storage amounts as needed. (Compare storage products.)

It'll be competing in a market with the start-up Nirvanix and Amazon S3. Nirvanix offers the advantage of uploading 256-gigabyte files, while Amazon and Rackspace allow file sizes of only 5 gigabytes.

Rackspace, which is also filing for an initial public offering, is targeting CloudFS at developers and businesses that want to "securely store a virtually unlimited amount of data on the Web connected through Rackspace's infrastructure," the company states.

This is a departure from Rackspace's usual model of customers using dedicated hardware, says Rackspace CTO John Engates. With cloud storage, customers typically don't know exactly where their data is being stored, and pay for space as they need it, like a utility.

Customers who already use Rackspace's hosting services can access cloud storage through Rackspace's private network, eliminating some of the latency inherent in accessing storage over the Internet. New customers can also access the service over the public Web.

Customers can sign up for a private beta here. Storage will start at 15 cents per gigabyte per month, with extra charges for data transfers for those customers accessing data over the Web rather than through Rackspace's own network. A public beta is scheduled to begin in the third quarter of this year. The cloud storage is initially being delivered only from Rackspace's Dallas data center, with another site in the United Kingdom likely to be added soon, Engates says.

Unveiling CloudFS is partly a defensive measure, because no one is sure yet just now prevalent cloud storage will become, either as a replacement of or a complement to traditional storage schemes, says IDC analyst Melanie Posey. But cloud storage is a natural move for Rackspace, which began offering server capacity in the cloud about a year and a half ago with Mosso, Posey says.