1. A disk array device comprising: a plurality of input/output channels that receive data input/output requests from at least one external device; a plurality of cache memories provided for corresponding respective input/output channels, each of the cache memories connected to each of the corresponding respective input/output channels; a disk drive device; a disk control module that performs data input/output to and from the disk drive device; at least one communication module that communicatively connects the input/output channels with the disk control module; and a control module that controls, upon receiving a data input/output request from the at least one external device, a sequence of execution of a first operation of a response processing to respond to the at least one external device according to the data input/output request and a second operation of a consistent order controlling processing to control and maintain consistency of data stored in each of the cache memories such that one of said first and second operations is executed first and the other of said first and second operations is executed second, wherein an analysis of the data input/output request is performed to determine whether controlling and maintaining consistency of data stored in each cache memory is necessary and said control module controls the sequence of execution with a result that said first operation is executed first if controlling and maintaining consistency is not necessary.