1. A system comprising: a first storage manager for managing storage operations in a first storage management system; a second storage manager for managing storage operations in a second storage management system, wherein the first storage management system and the second storage management system are autonomous from each other; a secondary copy of data generated in the first storage management system; a first computing device comprising a media agent that is a component of the first storage management system, wherein the media agent is associated with the secondary copy of data; a second computing device comprising a data agent and a registry key; wherein the registry key is received from the second storage manager, and wherein the registry key associates the data agent with the first storage manager for restore operations originating in the first storage management system; wherein the data agent is configured to operate in both: (a) a full-function client configuration in the second storage management system for participating in one or more storage operations for data generated by the second computing device which are managed by the second storage manager, and (b) a restore-only client configuration in the first storage management system, based at least in part on the registry key that associates the data agent with the first storage manager, wherein in the restore-only client configuration the data agent is configured to participate only in restore operations for secondary copies of data stored in the first storage management system which restore operations are managed by the first storage manager, including a restore operation in which the media agent and the data agent restore the secondary copy of data from the first storage management system to at least one of the second computing device and a second data storage device in communication with the second computing device, wherein the restored secondary copy of data is accessible to the second computing device as primary data.