Patent ID: 7468853

Claim:
A method of operating a disk array unit comprising a first housing and at least one second housing, the method comprising steps of: receiving an indication that a switch device changed from an ON position to an OFF position, and in response thereto: changing operating states of first storage devices in the first housing and in the at least one second housing from a READY state to a POWER-SUPPLY-OFF state whereby each first storage device substantially does not consume any power; reducing a number of operating fans of a fan unit disposed in the at least one second housing; changing operating states of one or more second storage devices in the at least one second housing to a NOT-READY operating state, wherein each of the one or more second storage devices does not respond to data I/O requests but does respond to non-data I/O requests; ceasing operation of a fan unit disposed in the first housing by removing power therefrom; and ceasing operation of third storage devices in the first housing by removing power therefrom.