1. In a storage area network (SAN) of the type having one or more digital data processors and having a plurality of storage devices, the improvement comprising: at least a first one of the digital data processors in communication access with at least a first one of the storage devices, the first digital data processor having a file system that effects access to that storage device, a manager, in communication with the first digital data processor, that responds to a request on behalf of the first digital data processor for extension of the file system by assigning a further storage device to the first digital data processor. an agent associated with the first digital data processor that responds to the assignment by extending the file system to include the assigned storage device.