A storage apparatus includes: a plurality of microprocessors; a plurality of storage areas formed into a drive group constituted from a plurality of physical drives; and a control unit for managing one of the microprocessors, which takes charge of data input to and output from one or more storage areas of the plurality of storage areas, as a microprocessor having ownership of the one or more storage areas; wherein the microprocessor executes dump processing for having an external physical drive store data of the one or more storage areas, for which the microprocessor takes charge of the data input and output, in response to a received I/O request; and wherein the control unit transfers the ownership of the microprocessor according to processing load bias of the dump processing which the plurality of microprocessors take charge of.