1. A method comprising: executing, in a storage management system, a unified-snapshot job that generates at most one snapshot for a logical unit number in a plurality of logical unit numbers regardless of the number of clients that store primary data to the respective logical unit number, wherein a storage array hosts the plurality of logical unit numbers; wherein the executing of the unified-snapshot job comprises: discovering, by a storage manager that manages the storage management system, a first subclient of a first client, wherein the first client generates first primary data that is stored to one or more logical unit numbers in the plurality of logical unit numbers, and wherein the first subclient represents a logical grouping of part of the first primary data, and discovering, by a media agent component of the storage management system, a first logical unit number in the plurality of logical unit numbers, wherein the first logical unit number comprises data of the first subclient; registering, by at least one of the media agent and the storage manager, a first association between the generated snapshot and the first subclient; and generating, from the snapshot and not from the primary data stored in the first logical unit number, a secondary copy of the first subclient data.