Abstract: A disk array apparatus is provided which, without stopping its host system, reconstructs data areas of its configured storage devices by determining optimum array parameters in keeping with disk access trends. Each of the storage devices includes a data area furnished in units of a stripe size, a log storage area for storing access logs, and a work area in which to change the data area. The inventive apparatus comprises: an access log storing means for storing access logs to the log storage areas; an access log analyzing means for analyzing trends of access to the storage devices based on the access logs; an array parameter judging and changing means for judging the validity of array parameters based on the result of the analyses and for setting optimum array parameters anew as needed; and a reconstructing means for reconstructing the data areas as per the changed array parameters.