Content Aware Storage (CAS) are specialized storage devices for managing information. CAS was popularized by EMC with their Centura-branded product line. Standard storage is able to refer to stored data by adressing location on a disk, usually a physical location on the disk drive. CAS uses a technique that allows information to be stored and referred to via a content address. Software communicating to a CAS device needs to refer to content identifiers when addressing stored data. The CAS device then maps the content id into the physical location on the disk where the information is stored. Any change or updates to the information on CAS will cause new content ids to be created. Often CAS devices do not allow information to be edited or deleted, only for new information to be added, a useful feature in applications targeting compliance because once information is stored, it can’t be tampered with.CAS is particularly well suited for applications that house fairly static information. The technology is slow and wastes space in applications when frequent updates are performed and versioning of information is not a requirement.When information is added to the CAS, a hash algorithm is run across the data set, producing a unique address for that component of information. If you were to attempt to store the identical data set for the information, the same hash would be produced, and that content id would be returned. In that case a single copy of the information resides on the disk, a useful feature if archiving, for example, emails for an entire organization that may contain large attachments that were replicated when sent to many of the same users in the organization.CAS has been around for a while now, and as you’d expect, the industry is evolving yet another technology from these roots, XAM (eXtensible Access Method). Like anything else, CAS products have been introduced by various vendors that are unique and incompatible. XAM is an attempt by the industry as a whole to define a standard interface to addressing information stored across CAS products from competing vendors.The goal of XAM is to provide a universal way to address information and metadata across CAS devices. XAM started in late 2005 by the SNIA (Storage Networking Industry Association). But not only will XAM provide interoperability of devices, it also standardizes the defintions and semantics related to retention, archival, and discovery. Standard techniques for handling metadata will assist with ensuring long-term archivals.The XAM working group is staffed by 95 individual members and 34 companies from storage vendors, application providers and end users. The initial specification is expected to be published in late 2006. It is expected that introduction and acceptance of XAM will increase the popularity of CAS products because of the device interoperability that it will provide.