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The Case Against CAS

Content addressable storage (CAS) is getting a reputation and it's not one to be envied.

Over the last couple of years, a handful of vendors led by EMC have launched products that create searchable, object-oriented repositories of fixed-content data. In markets like healthcare, where medical images like scans must be saved indefinitely, CAS seems a key solution.

Yet even as CAS has proliferated with the launch of EMC's Centera in 2002 and the advent of startups like Archivas, Bycast (which OEMs its medical CAS system to HP and IBM), Nexsan, and Permabit — some are crying foul. (See CAS Conundrum.) CAS, they say, is just another invitation to vendor lock-in.

There are several complaints: Most CAS systems don't run on heterogeneous hardware. Once you buy from one vendor, you can't add another. CAS isn't as open as it should be. It's still tough, for instance, to get a system that creates policies for moving data from one area of storage to another without APIs. Tape storage isn't always supported. Retrieving data can be iffy and performance is an issue.

Indeed, CAS has been controversial enough that some vendors have resisted the term in their marketing. (See Archivas Seeks Archiving Action.) Still, the negative publicity surrounding CAS has also encouraged counterclaims.

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