A controller (56), for use in a storage device (44, 114) of a data processing system (20, 90), includes a host interface (68), a memory interface (60) and one or more processors (64). The host interface is configured to communicate over a computer network (28, 98) with one or more remote hosts (24, 102) of a data processing system. The memory interface is configured to communicate locally with a non-volatile memory (52) of the storage device. The one or more processors are configured to manage local storage or retrieval of media objects (80) at the non- volatile memory, and to selectively compute metadata (84) that defines content characteristics of media objects that are stored, or that are to be stored, in the non-volatile memory.