1. A storage system comprising: a plurality of physical disks storing data; a storage controller providing a logical volume prepared on the plurality of physical disks and analyzing an access pattern of an access request to the logical volume from a host system or an application in the host system; and a memory storing access pattern table; wherein the storage controller selects a control method according to the analyzed access pattern, and monitoring processing of the access request based on the selected control method; wherein if the processing of the access request is improved by the selected control method, the storage controller stores relationships among an identifier of the host system or the application, the logical volume, the analyzed access pattern and the selected control method in the access pattern table; wherein the storage controller controls processing of the access request to the logical volume from the host system or the application by referring to the access pattern table; and wherein when the analyzed access pattern is that an access cycle comprised by writing data and then reading data and then writing data, the storage controller selects a first control method for destaging data from a cache memory after performing the access cycle.