Abstract: A magnetic disk control system includes a table for storing assignment information for assigning one of said first and second magnetic disk drives as a master disk for data I/O operations and the other as a spare disk for backing up said master disk, a copying section for executing data copy from the master disk to the spare disk, assignment information updating section for, when the data copying unit complete data copy from the master disk to the spare disk, exchanging the assignment information on the magnetic disk drive as a data copy source and the magnetic disk drive as a copy destination, and a operation check section for executing an operation check for maintenance for the disk drive newly assigned as the spare disk.

Abstract: In a data processor performing an input and output paging function, a main memory (MMU) and an input and output processor (IOP) connected to the MMU through a bus are provided. The MMU stores a list-service page table for mapping a logical space in which channel command entries are located, and a data service page table for mapping the data transfer areas specified by channel command entries, pointers for the respective page tables, and flags for the designation of a physical or logical address. The IOP reads the pointers from the MMU, refers to the respective page tables, determines whether the specified address is physical or logical, and translates it into an effective address.

Abstract: In response to a command including file extent information defining a file area received from a host processor, a disk cache processor stores the file extent information in an extent table and reserves a corresponding area in a disk cache buffer. In response to a WRITE command, the processor stores the data in the corresponding reserved area of the disk cache buffer and sets a write flag of the corresponding entry of a cache directory. When the processor is idling, it writes to a disk unit the data in the disk cache buffer which has not yet been written to the disk unit, and resets the corresponding write flag. In response to a command received from the host processor which has file extent information and designates a logical termination of a program, the processor writes all of the not-yet-written data which corresponds to the file area indicated by the extent information.