Executive summary

Terms like "SAN" and "NAS" become loaded with artificial and sometimes arbitrary meaning in the absence of a single, simple model for shared storage architectures. The SNIA Technical Council has developed a framework that captures the functional layers and properties of a storage system, regardless of the underlying design, product, or installation.

Much like the OSI 7-layer model in conventional networking, the SNIA Shared Storage Model may be used to describe common storage architectures graphically, while exposing what services are provided, where interoperability is required, and the pros and cons of each potential architecture.

The model describes architectures, but it is not itself an architecture. You cannot buy it, or a system that it describes by specifying it in a bid, or a request for a bid. You cannot "build it." The model does not represent any value judgments between the architectures it describes. Instead, the model makes it possible to compare architectures, and to communicate about them in a common vocabulary.

For example, the term "virtualization" is sometimes used to refer to some or all of the aggregation, mapping, and naming functions described here. Because there is a lack of clarity in the storage industry as to the precise meaning of this term we have deliberately avoided its use in the SNIA Shared Storage Model. Instead, we offer descriptions of what is meant at the various layers of the model, and adopt appropriate terminology for each of those meanings.

By aligning on such a common "architecture vocabulary," vendors can better explain the differentiation offered by their products, customers can better structure their choices and, for the first time, reference comparisons between common solutions will be possible.

This paper provides:

• An explanation of the context and scope of the model.

• A description of the model itself.

• Examples of applying the model to a number of different existing systems, to help explain how the model is used.