A virtual data storage system stores data as data objects to a plurality of storage devices in accordance with storage management policies. The system manages multiple copies of stored data objects on multiple media types over time. Storage pools define groups of media 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. A rule defines a destination storage pool, a length of time that the data objects are to remain in the destination storage pool, and a data source for the data objects. Copy and delete actions are performed to manage copies of data objects among the storage pools in accordance with the policy.