Abstract: When file and command management means in a secondary storage system is instructed to store a new file by a command containing file identification information from a host computer, the means transfers it to new file address determination means, which then references a disk management table to find a free area and considers characteristics of the file, the configuration of the secondary storage system, etc., to determine an optimum area as an area for registering the new file. Also, the address of the determined area is related to file identification information of the file and a correspondence therebetween is registered in a local file management table. The file and command management means stores the file in the determined area in a disk unit via a disk unit controller. Then, file placement optimization can be carried out independently of the type of secondary storage system.