A method and apparatus for assuring data consistency in a data processing network
including local and remote data storage controllers interconnected by independent
communication paths. The remote storage controller or controllers normally act
as a mirror for the local storage controller or controllers. If, for any reason,
transfers over one of the independent communication paths is interrupted, transfers
over all the independent communication paths to predefined devices in a group are
suspended thereby assuring the consistency of the data at the remote storage controller
or controllers. When the cause of the interruption has been corrected, the local
storage controllers are able to transfer data modified since the suspension occurred
to their corresponding remote storage controllers thereby to reestablish synchronism
and consistency for the entire dataset.
