Born from a research project at the University of California, RAID has become one of the mainstays in storage networking. While other storage technologies have become obsolete since RAID was invented, RAID has become increasingly useful through its ability to improve data availability, increase storage scalability, consolidate storage management, and boost I/O performance. At the core of RAID is the Boolean XOR function, which has the unique property of being its own inverse operation. This allows RAID to be implemented very efficiently in either hardware or software. It also means the various failure modes and their remedies use the same function in performing their work. Because RAID is defined primarily by algorithms, it can be implemented in many different ways and locations in the I/O path. Today, RAID levels 1, 5, and 10 are commonly found in a wide variety of products, including system motherboards, host bus adapters, storage subsystems, and SAN switches/systems. |