A virtual data storage system stores data as data objects to a plurality of storage devices in accordance with storage management policies. Storage pools define groups of medial that are to be treated in a uniform manner. A policy is composed of a series of policy copy/delete rules that direct movement of data objects into the storage pools. Copy and delete actions are preformed to manage copies of data objects among the storage pools in accordance with the policy. As an extension of the storage management policies, the process of creating export media sets is automated. These processes can also be used to create backup media. When an export media set is created, subsequent commands are prevented from modifying the media in the export media set. When a backup is created, subsequent commands are prevented from overwriting media containing data referred to by the manifest media for the backup.