To provide an RAID for reducing a storage capacity required for the redundancy of data, and improving the security of data, and efficiently using a line.

Data are made redundant, and divided into a plurality of volumes, and a controller C for controlling the distribution and storage of the respective volumes in a plurality of storages S distributed and arranged through a network is provided with a path managing part 504 and a storage set managing part 505. The path managing part 504 calculates evaluation values indicating the values of the respective distributed and arranged storages as the objects to be used on the basis of band width, communication costs, and physical distances between a node for requesting writing and the storages. The storage set managing part 505 selects the plurality of storages as the optimal storage set from among the distributed and arranged storages on the basis of the evaluation values.