Data transfer control method and apparatus for external storage subsystem adapted to perform erasing after writing

摘要

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. Thus, the area of erasing and the number of times of execution are minimized and the throughput of the data transfer between the processing unit and the rotating storage device is improved.