NEC Storage StoragePowerConserver (power conserving function) is a product to reduce power consumption by activating physical disks not always used when necessary. While significance of reducing a load to the environment is increasing for realization of eco-society, power conserving function provides a basic function supporting power conserving operation in cooperation with business tasks by realizing a control function to deactivate and activate physical disks which consists a pool where a volume belongs, in accordance to usage of the volume. Operation to activate and deactivate a volume is also possible by command line interface (CLI), and power conservation operation in cooperation with business tasks can be automated.