To suppress power consumption, while maintaining a file sharing function in a system including a data storage device having a file sharing function.

A control unit 1404 of digital composite machine transmits, when shifting to a power-saving condition, identification information (file name, pass information or the like) of data to be stored in a shared file storage unit 1406 to another data storage device of a standby condition present in a network 100, in order to shift to the power-saving condition. When there is no other data storage device in the standby condition in the network 100, the control unit 1404 refers to a standby power management table stored in a data storage unit 1405, starts the other data storage devices an amount of power consumption of which is lower than that of the own device, and transmits the identification information to the started other data storage device.

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