Abstract: In control method and apparatus for data transfer in an external storage subsystem, a disk unit and a control unit interposed between a host channel and a processing unit are provided and data in a variable record length supplied from the host is converted to data in a fixed record length to write it in the disk unit. Final format writing end position information for a logical track and an erase flag indicating whether the erasing is required or not are stored at a portion of a logical track control table which controls a cache memory, for each logical track. In the format writing on the cache memory, the final format writing end position information and the erase flag are updated, and when the data is written into the disk unit from the cache memory by logical track unit, the erase flag is referred and the erasing is performed if it is required.

Abstract: A storage system comprises a disc drive unit including a plurality of logical drive groups each having a plurality of physical drives, and a disc drive control unit for controlling the information transfer between the disc drive unit and the host system. The logical data arriving from the host system is divided into a plurality of continuous data blocks, from which redundant data is prepared for data restoration. The redundant data is added to the continuous data blocks to provide updated logical data. The storage system is controlled in such a way as to write the updated logical data into a plurality of physical drives. In the case where a fault develops in any of the data blocks of the physical drives to be accessed, redundant data is generated from the updated logical data.