Abstract: Track positioning of a scanning tape head in a helical tape system may be adversely affected by relative offsets between elements in read element pairs and in write element pairs accessing synchronization patterns. Compensating for variations in the position of read and write elements accessing a given pair of data channels is accomplished by using the relative offset of the first detected synchronization patterns in each pair of data channels as a measure of the relative locations of write elements producing the synchronization patterns and read elements accessing the synchronization patterns. This relative offset is then used to correct subsequent synchronization pattern readings taken from the data channel pair.

Abstract: A disk storage system that writes multiple copies of records directed to user-specified volumes. A plurality of spaced apart control units interconnected by direct data links and a corresponding plurality of sets of recording means communicate over the direct data links when a write request is received by one control unit to cause one volume in each set of recording means to write a copy of the received record.