Content-addressed storage (CAS) systems locate items by unique identifiers based on the content itself rather than...
its location in storage. This is different from data deduplication, which scans block-level data for duplicate blocks and replaces duplicates with pointers to the original copy of the block.
When an object is stored in a CAS system, its content is scanned and an identifier, such as a hash value, is generated and then used to retrieve the object as needed. Because each object's identifier is based on its content, it's easy to verify that the retrieved object hasn't been changed since it was stored, which makes CAS a good fit for compliance-related storage. But that also means any change to an object stored in a CAS system creates a new object that's stored separately, so CAS is best suited to data that won't change once it's saved.
When you're considering CAS, remember that storing an object in a CAS system requires more time and computing power than storing it in a conventional file system.
For the full feature go to http://searchstorage.techtarget.com/tips