The RAID Advisory Board is set to replace the long-established set of seven RAID Redundant Array of Inexpensive Disks technology levels with a new classification scheme, emphasizing the practical functionality of systems rather than their underlying technology. The Advisory Board membership, under chairman Joe Molina, will meet in Colorado Springs on July 17, and is expected to vote in the new six-level scheme, most of the details of which have already been hammered out over the past few months. RAID levels 0 to 6 will subsequently be referred to from a historical standpoint only, and RAID level conformity logos for the original levels will no longer be issued. The new levels, if accepted, will consist of three main categories and three sub-categories. At the low end is Failure Resistant, described as pure RAID: if a disk drive fails the data is preserved and access to the data is maintained in a timely way so that an application will still run at acceptable performance levels. Failure Tolerant is the middle category, where all of the components within a system must be redundant. At the high end, Disaster Tolerant describes a disk system that is zoned, enabling the other zones to take over seamlessly if one is destroyed. Each of the three categories can have a plus mark appended to it to signify additional functionality. For example, Failure Tolerant+ adds a requirement for the provision of an additional external power sour-ces, and Disaster Tolerant+ specifies that each zone must be at least six and a quarter miles apart. Although they seem like they have been around for ever, the original five RAID levels were first defined in 1988 by David Patterson, Garth Gibson and Randy Katz in the Berkeley paper A Case for Redundant Arrays of Inexpensive Disks. Levels 0 and 6 were added later. Over the years, vendors weighed in with their own extensions, mainly to improve input-output performance and provide high availability, and things became somewhat confused. Storage Computer Corp, for instance, trademarked the name RAID 7, while EMC Corp opted for RAID-S. Following the July meeting, the Advisory Board will expand its performance and functionality testing to fit in with the new classification.
