1. Field of the Invention
The present invention is related to a power device and a power device power supply method capable of being used, for example, in a storage controller.
2. Description of the Related Art
A storage controller comprises a storage unit, which connects a large number of hard disk drives in an array, and provides a logical storage area (logical volume) to a server or other such host computer (hereinafter “host”).
To heighten reliability and availability, the storage controller provides a host with a redundant storage area based on RAID (Redundant Array of Independent Disks). The storage controller also makes various resources, such as a microprocessor and communications channel redundant. In view of such high reliability and high availability, the power device of the storage controller is also made redundant.
Accordingly, in the prior art, a DC/DC converter is built into each hard disk drive (Japanese Laid-open Patent No. 2004-126972). Thus, in the prior art, even if a power failure occurs in one of the hard disk drives, this power failure is prevented from affecting the other hard disk drives.
In the prior art described in the above literature, since a DC/DC converter is built into each hard disk drive, each DC/DC converter must be capable of outputting power proportional to the maximum power consumption of each hard disk drive. Therefore, it is necessary to provide DC/DC converters, which have sufficient output performance, for the total number of hard disk drives, raising power costs. Further, since it is necessary to provide the same number of DC/DC converters as the number of hard disk drives, the number of components and inventory increase, and power productivity decreases.
Since the output capacity of the respective DC/DC converters is set in accordance with the maximum power consumption of the respective hard disk drives, it is also necessary to increase the output capacity of AC/DC converters for respectively supplying direct-current power to the DC/DC converters. Thus, power device costs increase, and the size of the device also becomes larger.
Further, in the prior art, because each hard disk drive has a built in DC/DC converter, it is impossible to operate a hard disk drive when a power failure occurs in a DC/DC converter.
Additionally, in the prior art, each hard disk drive respectively comprises only one DC/DC converter, and the DC/DC converter does not have a redundant constitution. Therefore, it is impossible to replace the DC/DC converter alone.
Further, in the prior art, when a power failure occurs, it is not possible to specify whether the cause is a DC/DC converter failure, or whether the cause is a failure of another circuit inside the hard disk drive. Therefore, the entire hard disk drive must be replaced when a power failure occurs.