Patent ID: 8255715
Filing Date: 2012-08-28
Classification: G06F,G11B,Y02D

Abstract:
1. A storage system comprising: a plurality of storage devices for storing data; and a controller connected to a host computer via a network for identifying access from the host computer, specifying the storage devices which should become targets of the access from among the plurality of storage devices, sending/receiving data to/from the specified storage devices, and controlling the plurality of storage devices according to a plurality of power modes; wherein the controller selects, as the power mode, any one of the power modes including a normal mode, which makes each of the storage devices capable of processing an I/O request from the host computer, and a plurality of power-saving modes which make each of the storage devices incapable of processing an I/O request from the host computer and operate in a power-saving state with less power consumption than in the normal mode, wherein in the process of controlling each of the storage devices according to the selected power mode, the controller selects the storage devices, which should be controlled in any one of the power-saving modes, from among the storage devices operating in the normal mode in the plurality of storage devices, and before shifting to control the selected storage devices in any one of the power-saving modes, the controller sets a combination of power-saving modes that satisfies return conditions from each power-saving mode to the normal mode; and then the controller controls the selected storage devices in the set combination of power-saving modes; wherein before shifting to control the selected storage devices in any one of the power-saving modes, the controller calculates a time and an electric power required to have the storage devices return from each of the power-saving modes to the normal mode; and based on each of the calculation values, the controller sets a combination of power-saving modes that satisfies the return conditions defined by a host timeout period of an I/O request and supplied power, wherein the power-saving mode is selected for a particular storage device such that the particular storage device can respond within a host timeout period to an I/O request sent from the host.