The invention provides a storage area network (SAN) of type having one or more digital data processors coupled to one or more storage devices. At least a selected one of the hosts includes a file system that effects access by the host to assigned storage devices. This can be, for example, a conventional AIX or other host platform file system that oversees file and other data accesses between the host and those assigned devices. That host can be associated, according to these aspects of the invention, with lower and upper capacity bounds for purposes of file system extension. In response to a request by (or on behalf of) the selected digital data processor for extension of the file system, the manager assigns one of more further storage devices to that digital data processor.