Online storage provider SpiderOak on Tuesday will begin offering businesses a way to enjoy its cloud backup, sync, and sharing service from behind a firewall, through an enterprise service called SpiderOak Blue Private Cloud.

SpiderOak launched in 2007 as a cloud storage solution for consumers, the same year as Dropbox. The online storage market has since become rather crowded, with leading platform companies getting into the game. Apple iCloud, Google Drive, and Microsoft SkyDrive are now vying with Dropbox, Box.com, SpiderOak and others to store users' files on their servers.

SpiderOak, however, is one of the few online storage providers--Wuala is another--that supports "zero-knowledge" privacy: Its client software encrypts data for storage but does not provide a copy of the encryption key, so SpiderOak cannot access client data. Most other online storage services, particularly in the consumer market, retain copies of encryption keys and thus may be required to provide access to client data to comply with law enforcement demands or may lose control of the key if hacked.

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"Just because your data is online, doesn't mean it can't be private and secure," said SpiderOak CEO Ethan Oberman in a phone interview.

Such privacy may be appealing to consumers who care passionately about privacy, but it is often a requirement for large companies, particularly in regulated industries. At the same time, corporate data regulations may also require that data is stored in a specific place--inside the company or outside a specific jurisdiction.

Some companies, for example, say they cannot under any circumstances have data stored on U.S. soil, due to the Patriot Act, explains Oberman.

One early SpiderOak Blue Private Cloud customer is the Department of Defense. Oberman says he can't discuss specifics of the deployment at the moment but notes that over 10,000 users are presently involved and that the deployment is likely to serve over 100,000 users eventually. "It's pretty significant," he said.

SpiderOak Blue Private Cloud doesn't exactly fit the definition of cloud computing: It's not elastically scalable; it's a 10-machine RAID-6 cluster, a box of servers provided by SpiderOak or by the customer on existing infrastructure. Either way, it doesn't offer storage capacity that can expand and contract on-demand, like SpiderOak Blue Hosted Storage, introduced earlier this year.

But it retains other characteristics of cloud-based storage, like easy internal and external file sharing, rapid deployment, directory integration, single-sign on, administrative controls, usage reports, and options for retention of deleted files.

In hosted form, Spider Oak Blue costs $600/TB per month. For the on-premises private cloud, the cost is $5/user per month.

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