1. A tangible computer-readable storage medium whose contents cause a data storage system to perform a method for archiving multiple data objects included in primary copy data, the method comprising: receiving, from a client, both full and incremental backup copies of the client's primary copy data; using the received backup copies to create a secondary copy of multiple data objects included in the primary copy data; for each of the multiple data objects for which a secondary copy was created, adding an entry for the data object to a data structure, the entry including an identifier associated with the data object; after creating the secondary copy, identifying one or more of the multiple data objects that satisfy predetermined archival criteria; and, for each of the identified one or more data objects: looking up the identified data object in the data structure using the identifier associated with the identified data object; receiving a token for the identified data object; and replacing the identified data object in the primary copy data with a stub referencing the secondary copy of the identified data object, wherein the stub comprises the token.