In order to efficiently use each of storage physical devices fast in access rate for each data block even where a deviation in access frequency exists within a file, in a storage system comprising a plurality of the storage physical devices, a policy is stored within the storage system in advance with respect to the placement of file's data blocks, and data of each file is evaluated with respect to the policy upon storage of the file's data blocks. A decision as to in which storage physical device the corresponding data blocks should be located, is made based on the evaluation result of the policy.