A data storage library system and a method for storing, and maintaining and
tracking synchronism between, multiple copies of identifiable data volumes
between hosts and a plurality of data storage libraries, and transparent
to the hosts. The library controller of each library provides an updatable
synchronization token directly associated with each data volume. A
plurality of directors are provided, each separate from and coupled to the
hosts and each separate from and coupled to each data storage library.
Each director responds to ones of separate, partitioned access addresses
addressed by the hosts. The responding director supplies each data volume
supplied from a host to all of the data storage libraries, and updates
each synchronization token directly associated with the supplied data
volume. Thus, the directors store duplicate copies of the data volume in
the data storage libraries without involvement by the host. The currency
of the data volumes are each tracked by means of the directly associated
synchronization token, and the synchronization token is not tracked by the
host nor is a central tracking database required.