Method for physical backup in data logical order

This invention is directed towards data storage systems, and more particularly towards backup and restoration of data residing in data storage systems. A system for providing high speed external backup and restoration of data in a data storage system. Individual data objects are backed up in logical order on backup media such as magnetic tape so that they may be retrieved individually. Minimized descriptions of backed up data are transmitted between the host and backup systems to control high speed transfer of data between data servers and backup devices on a separate data channel. The descriptions are manipulated by the backup system to comply with formats of any number of host systems and data storage systems and to efficiently map the backed up data onto the backup devices. The system also provides for restoration of data to the data storage system by using a host system to pre-allocate space for the restored data, obtaining mapping information for the allocated space from the host system, and then directly writing the restored data into the allocated space, based on the mapping information.