Storage system and method of control

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. The data block of the updated logical data of the physical drive corresponding to the data blocks that has not developed a fault, among the data blocks and the redundant data making up the updated logical data, is stored in the physical drive. The data block of the updated logical data of the physical drive corresponding to the data block that has developed a fault is stored in the nonvolatile memory. The completion of writing the updated logical data into the storage system is reported to the host system. In re-updating the updated logical data, the data block of the re-updated logical data corresponding to the data block of the physical drive that has developed a fault is stored in the physical drives. The data block stored in the nonvolatile memory are stored into an alternate block allocated to the physical drives.