A storage apparatus has a plurality of hardware engines which send and receive information to and from a controller, which, on the condition of acquiring a request command from a host, determines identifying information of the request command, executes data I/O processing to the storage device according to the request command when first identifying information has been added to the request command and when second identifying information has been added to the acquired request command, transfers the request command to the hardware engine, acquires the data requested by the hardware engine from the storage device and transfers the acquired data to the hardware engine. The hardware engine acquires and analyzes an add-on command from the host and according to the request command, requests the controller to transfer the data based on the analysis result, and thereafter executes processing to the data transferred by the controller according to the add-on command.