Provided is a highly reliable disk array device. Specifically, this disk
array device has a number of hard disk drives for respectively storing
data, and which converts a first direct voltage supplied to each of the
hard disk drives via a common power supply bus into a second direct
voltage required by the hard disk drives at each of the hard disk drives,
wherein each of the hard disk drives includes a voltage converter for
converting the first direct voltage into the second direct voltage; a
control unit for controlling the voltage converter so as to suppress the
fluctuation of the second direct voltage based on the second direct
voltage output from the voltage converter; and a response characteristics
switching unit for switching the response characteristics of the control
unit against the fluctuation of the second direct voltage so as to
improve the response characteristics of the control unit against the
fluctuation of the second direct voltage when a transitional voltage
fluctuation of the second direct voltage occurs.