Partial migration of an object to another storage location in a computer system

A technique is provided whereby a stream of data located in a first storage location is registered for migration administration and according to preset criteria, portion(s) of the stream of data that are suited to another storage location are migrated to maximize system storage efficiencies. The file system may have use of facilities that enable the monitoring of files/streams that have been registered for migration administration or files/streams may be polled according to preset criteria. If the stream of data has portions to migrate to another storage location, the hierarchical storage management (HSM) system migrates the data to the other storage location, such as to long term or off-line storage, and preserves the data relationships of the stream via metadata. The technique allows for multiple volumes to be spanned by the migration target location, and multiple file systems may service the source and target.