EMC has unveiled a web-delivered version of its Atmos cloud storage service.

Launched in November 2008, Atmos is described as 'cloud-optimised storage' aimed at large businesses that need to manage information on a global scale while giving staff worldwide access to content.

Atmos customers manage their storage by setting levels of policies, but EMC said that customers will now be given increased flexibility by being able to manage some of their data online.

"Some people think that cloud and internet go together, but this is not accurate," said Mike Feinberg, EMC Cloud Infrastructure Group senior vice president, at the EMC World event in Florida today. "Cloud is an architecture and is on-demand, but a large number of customers are now interested in getting internet access."

Feinberg explained that not all business information can be stored through an internet-delivered service because some data needs to be kept behind a firewall. Organisations can generally store around 20 per cent of their corporate data online, he added, but this is likely to grow in the near future.

A key capability of Atmos Online is allowing customers to move, or 'federate', from on-premise to online Atmos clouds. For example, a customer can set policies to federate their information to an external Atmos storage cloud for cost efficiencies and collaboration, EMC said.

The company is using data leakage prevention policies derived from its RSA division to allow customers to tag information according to where they want it to be stored.

Benjamin Woo, an analyst at IDC, said: "It is clear that IT organisations have the desire to adopt cloud storage technologies. It is also clear that they must maintain the necessary controls over where their data resides, while preserving the investments of existing applications and infrastructures."

EMC Atmos Online will be made available as a package, or bit by bit, as customers require.

"The online service demands no commitment from customers; they can pay by credit card like for cellphone minutes," said Feinberg.

Atmos runs on industry standard x86 servers and has a storage capacity of up to 360TB, but EMC has argued that the storage capability is at a petabyte, rather than terabyte, scale.

"Petabytes should not all be treated in the same way," said Feinberg, adding that this is why EMC offers a choice of online and on-premise storage offerings.

Datacentres supporting Atmos are all based in the US at the moment, but EMC has plans to expand these to Europe.