Disclosed is storage system, that is, an array-type disk apparatus which is provided with an error monitor section which monitors the status of error occurrence in a disk drive and instructs initiation of mirroring between the disk drive and a spare disk drive when the number of errors occurred of the disk drive exceeds a specified value, and a mirror section which performs mirroring between the disk drive and spare disk drive. Storage system, that is, the array-type disk apparatus may be provided with an error monitor section which monitors the status of error occurrence in a disk drive and gives such an instruction as to set the status of the disk drive in a temporary blocked state, and a data restoring section which executes data restoration by reading data from the temporary blocked disk drive when reading from another disk drive constituting a disk array group is not possible during data restoration.