Patent ID: 8271749

Claim:
A storage subsystem comprising: a plurality of hard disk drives; and a controller configured to execute a plurality of commands received from a host computer coupled to the controller for the plurality of hard disk drives and to determine whether each received command is a priority command based on priority command information that defines attributes of command, and wherein, for each received command, upon determining that the received command is not a priority command, the controller adds the received command to a non-priority command queue, wherein, for each received command, upon determining that the received command is a priority command, unless a quantity of priority commands to be executed during a predetermined time period is greater than a predetermined value, the controller executes the received command in preference to each received command to be executed during the predetermined time period in the non-priority command queue, and wherein the controller successively executes each received command to be executed during the predetermined time period that is determined to be a priority command in preference to each received command to be executed during the predetermined time period in the non-priority command queue within said predetermined time period until said predetermined value of priority commands have been executed.