Abstract: A method and system for enhancing the efficiency of data accessing within a storage subsystem which is coupled to a host system via a storage subsystem controller and a data channel. The storage subsystem controller preferably includes a tracked cyclic storage device which has multiple disks which are rotatable about a single spindle. Recording tracks within each disk are then accessed utilizing multiple switchable transducer heads. A signal transmitted from the host system is utilized to define a sequence in which a group of recording tracks are to be accessed. That signal is then utilized to create a transducer head switching table within the storage subsystem controller which lists each recording track to be accessed and an associated control parameter for selecting a particular transducer head to be utilized to access a subsequent recording track.

Abstract: A direct access storage device (DASD) system uses a read/write head having a wide transducer write element and a narrow magneto-resistive read element. In order to avoid mistakenly reading a incompletely erased old data field, the system uses a verification procedure. Data are read at two positions along the data track which are separated by a radial distance D. This distance D is selected to be greater than the width of any incompletely erased data record. If the data read at the two read positions are equal, then the data are deemed to be correct and are sent to a host system.