Abstract: Examples of methods, systems, and computer-readable media for migration of data, including data from archives, are described. In some examples, the archive data may be divided into slices which may be indexed and queried on a per-user basis to facilitate a per-user migration of the archive data. Example techniques are described for migrating archives that employ storage saving techniques. When an extraction fails for lack of a copy of a particular file in a slice, the missing files may be systematically identified and re-processed. Examples are described of methods, systems, and computer-readable media for aggregation of multiple mailbox descriptor files to migrate multiple mailbox descriptor files to a single destination mailbox.