• They are clustered designs that can be scaled horizontally
• Physical location of files is abstracted, allowing transparent migration & healing.
• They tend to heal themselves, reducing the need for service
• When a file is stored, they generate their own unique name for the file.
• The primary access model is via API, although secondary access via file systems is often supported
• They are immutable (files cannot be modified)

There is nothing in these valuable benefits about hashing or hash algorithms. These are the properties of Object Archival Storage Systems, which is a far more appropriate way of describing the breed. Dare I propose a new acronym OASS? Well the SNIA committee charged with standardizing these things is working hard on their own answer, and I'll defer to them. They used to call themselves CAS Solutions Initiative (CASSI), but they too have seen the light.

*A point of fact, but none of the CAS systems on the market today are actually CAS. CAS implies that the stored objects are accessed using a hash value computed from the file's contents. But there are not commercially available systems that do this today. For example, EMC's Centera uses a "C-clip" as the object handle, which is an amalgamation of a metadata record and the object hash. Other CAS/OS systems may use other more reliable ways of creating unique object identifiers that have nothing to do with the hash value.

So it would seem that the term "CAS" is meaningless, and we all hope it dies. But Object Storage is here to stay due to its propensity to solve unsolved problems of scale, reliability, and TCO. Somewhere in there is a role for computing hash values, but that feature will be less and less visible to customers, especially as Object Storage moves into a primary storage role.