1. A method for using deduplication in a storage management system to provide an application executing in the storage management system with access to a file system that appears to be of virtually unlimited capacity, the method comprising: executing a pseudo-file-system driver on a client computing device that hosts a data agent component of the storage management system, wherein the data agent is associated with the application, which is installed on the client computing device; instantiating the file system, by the pseudo-file-system driver, based on exposing a first mount point for the file system, wherein the file system is stored to a primary storage device associated with the client computing device; configuring, by the pseudo-file-system driver, an association between the file system and a corresponding deduplication database component of the storage management system; and executing the application, by the client computing device, wherein the pseudo-file-system driver provides the application with access to the file system characterized by virtually unlimited capacity based at least in part on the pseudo-file-system driver invoking at least one deduplication job, and wherein the at least one deduplication job (i) moves some data from the file system in the primary storage device to a secondary storage device component of the storage management system, and (ii) stores the moved data in deduplicated form thereto based at least in part on the deduplication database.