Techniques for cooperative storage management are described. According to embodiments described herein, a storage server stores backup data for a plurality of client systems, including a first client system and one or more other client systems. The storage server receives a request from the first client system to store new backup data. In response to the request from the first client system, the storage server determines which backup data to delete to make space for the new backup data based, at least in part, on retention duration goals associated with the one or more other client systems. The retention duration goals indicate that the client desires to be able to recover data at least as old as a specified age. The storage server may also determine which backup data to delete based, at least in part, on respective minimum space parameter values for the other client systems.