A storage management system, if the required response performance of the file is added to the access request from the host computer, compares the required response performance of the file with the response performance of the pool volume assigned to the page. If the response performance of the compared pool volume does not satisfy the required response performance, the storage management system selects a pool volume whose response performance satisfies the required response performance from the pool volumes, migrates the page to the selected pool volume, and stores the data in the page to which the pool volume is assigned.