Pathing (sometimes called path control ) is a networking approach used to address the specific needs of storage networks (as compared to ordinary message networks) by changing the way that communication paths are managed and organized. Connection failures in message networks generally just mean that the connection must be retried; in storage networks, however, a failure is more likely to cause a system crash . Also, the margin for error is smaller for storage networks; whereas error recovery within minutes is acceptable for message networks, for storage networks it should be within seconds - and preferably milliseconds. Because of these differences, storage network routing must include redundant, well-defined paths, enable fast path changes, and have the altered topology information updated rapidly.
According to Marc Farley, author of Building Storage Networks , node routing provides more precise connection control than is afforded by switch es and routers. Message networks typically have a very large number of node s, any of which may have to connect to any other and connection requests are randomly designated. As a consequence, it is considered that routing activities would overload end nodes. In comparison, storage networks have fewer nodes and fewer connections, and connection requests are specifically assigned. In these conditions, it is possible for nodes to manage paths.
Pathing is among the most promising technologies behind the expansion of the storage market - which is projected by Adam Couture, senior analyst at Gartner Dataquest, to grow to $7 billion by 2003, up from $10 million in 1999. Storage area networks ( SAN s) and network attached storage ( NAS ) have arisen as solutions to the rapidly increasing need for storage of enterprise data. Originally, enterprise computers and storage devices had one-to-one relationships, not a practical arrangement for multi-user environments with complex data-sharing needs. SANs allow multiple computers to share a single storage device, with technologies like path control, mirroring, and virtualization used to meet the enterprise's needs for reliability and constant data availability.