DEVICE AND METHOD FOR CONTROLLING DISK

PURPOSE:To prevent the end of I/O processing in a master device from being delayed by allowing a control device to decide whether a command from the master device is being executed or waiting for execution and executing correcting operation in a state other than the execution waiting state. CONSTITUTION:The control device 2A is provided with a correcting operation request commanding part 21b, a correcting operation detecting part 20c, a correcting operation deciding part 20b, a correcting operation commanding part 20a, a commond processing control part 20d, and a detecting means 20e for detecting the execution or holding of a command. At the time of detecting an off-track correcting operation request, command execution or command holding is decided, and during the period of commond execution or command holding, command processing is continued or executed. In other cases, the off- track correcting operation of the disk device is instructed. Consequently, the generation of a long I/O execution waiting state in the master device 1 can be prevented.