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Just What Is 'Content-Addressed Storage'?

When a survey sponsored by EMC in 2000 found that 75% of the information in the world was "fixed content," it didn't take a prophet to recognize that technology for dealing with such data was in the pipeline.

"Fixed content" simply refers to data that is written once and never changed. It could be an invoice, a purchase order, a financial statement, archived e-mail, or a medical X-ray. It's information that needs to be stored but cannot be altered in any way. When you add in compliance for electronic record-keeping, which was spurred even further by new SEC regulations, a storage schema designed specifically for keeping fixed content secure and in place was inevitable.

Keeping data secure and available in accordance with any number of regulations is also big business. According to a study by the Enterprise Storage Group on the impact of compliance on information management, compliance-related storage products and services could be worth as much as $6 billion over the next four years.

EMC coined the term "content-addressed storage" (CAS) in 2002 when it released its Centera product. At its most basic, CAS provides a digital fingerprint for a stored piece of data. The fingerprint (also known as an ID or logical address) ensures that it is the same exact piece of data that was saved. No duplicates are ever stored. It's a radical departure from the traditional file system used in most storage systems.

EMC's Centera is a backend used with any number of applications -- including popular, enterprise-class content managers from Documentum and FileNet -- thanks to an EMC partner program and APIs. Centera is a magnetic disk-based WORM device, and it's now available in a Compliance Edition, which is specially suited for enforcing retention periods for fixed content.

Tumbleweed Communications, one of EMC's Centera partners, uses Centera to archive electronic communications such as e-mail and instant messages for compliance with regulations. Artesia, a maker of digital asset management technology, has also teamed with EMC and will use Centera to archive rich media assets.

While CAS through Centera offers a solution for complying with the more than 15,000 federal and state laws dealing with record retention, what else can it accomplish? That's a question being asked by Anne MacFarland, an analyst with Wellesley, Mass.-based The Clipper Group.

"Compliance is the low-hanging fruit of the week," says MacFarland. But she has a hard time seeing other applications for content-addressed storage, and added that the term itself has relied mostly on the clout of EMC, a powerful name in the storage world.

Page 2: 'Searchability' May Be Key to CAS Growth