A system including plural storage devices provides a technique for controlling storage devices in which files are located by a file system, and turning on or off the storage devices based on prediction of the start or end of access to the files. A program that manages power to the storage devices and data access to the storage devices via the files includes means or functions for allocating a storage device as an area in which a file is located, for selecting a storage device in which a file is located, for predicting that access to a file is started for commanding turning on power to a storage device based on the prediction that access to a file is started, for predicting that access to a file terminates, and for commanding turning off power to a storage device based on the prediction that access to a file terminates.