1.  Technical Field
The present invention relates to an energy saving of a storage system. 
2.  Related Art
As a technology relating to an energy saving of a storage system, for example, the technology disclosed in JP-A-2007-156597 is known.  According to JP-A-2007-156597, in a plurality of disk drives, there are log drives forming a basis of a log storage area, and normal drives forming a basis of a data storage area.  The log drives operate in such a way that a data write is constantly possible, while with the normal drives, normally, a data write is not possible.  Write subject data from a host are written in the log storage area, after which, the normal drives being caused to operate, they are forwarded from the log storage area to the data storage area.