1. A system for sharing a media volume in a network, the system comprising: computer hardware comprising one or more computer processors; a first media agent that executes on the one or more computer processors, wherein the first media agent copies data associated with one or more storage operations to a media volume; a second media agent that executes on the one or more computer processors, the second media agent copies data associated with the one or more storage operations to the media volume, wherein the second media agent runs a listening process that monitors messages sent from a storage manager when the second media agent is in an inactive state; an index structure comprising multiple entries that associate different media agents with one or more media volumes, wherein at least one of the entries in the index data structure identifies that the first and second media agents share the media volume and that at least the first media agent controls the media volume; and a storage manager that executes on the one or more computer processors, the storage manager in communication with the first media agent and the second media agent, the storage manager configured to: direct the first media agent to enter a deactivation state with respect to the media volume; direct the second media agent to enter an activated state with respect to the media volume by communicating with the listening process of the second media agent, wherein in response the second media agent mounts the media volume and creates an access path to the media volume; and update the index data structure to reflect that the second media agent controls the media volume.