1. An object storage system comprising: a server adapted to communicate with users of the object storage system over a network; a plurality of data storage devices which store and retrieve data objects of the users and which are arranged into a plurality of locations; a storage controller associated with each location to direct data transfers between the associated data storage devices and the server using an existing map structure that describes the data objects in each location; and a management module adapted to generate a new map structure, migrate at least one data object from a first location described by the existing map structure to a second location described by the new map structure, and to distribute the new map structure to each of the storage controllers after the migration of the at least one data object.