Information processing apparatus and power supply method used in the apparatus

An information processing apparatus is operated by externally supplied DC power. The apparatus includes an external redundant power supply device including a plurality of power supply units each of which converts AC power into DC power, a housing which accommodates a plurality of devices, a DC power input terminal provided on the housing and configured to receive the DC power from the redundant power supply device, and a power supply circuit provided in the housing and configured to generate a power supply voltage, which is to be applied to each of the devices, from the DC power received by the DC power input terminal.