1. A disk array system, comprising a storage unit; and a controller that controls the storage of data in the storage unit, wherein processing concerning transfer of the data is carried out pursuant to requests received from other system connected through a communication means, wherein: the controller has a channel control unit that communicates with other system pursuant to an interface protocol and carries out data transfer processing; the channel control unit comprises a port unit that carries out communication processing pursuant to the interface protocol; and multiple host processor units that have processors which operate in conformity to the control of a channel adapter driver, wherein the multiple processors operate in parallel to control the operation of the port unit, and the channel control unit distributes processing that meets the request at the plural processors; wherein, when a request is received from the other system at the port unit, the first host processor unit which has a first processor among the plural processors decides a processor that takes charge of processing in accordance with the request based on the judgment of processing load condition of plural processors including itself with respect to the request received from the other system, and carries out processing as it is if the first processor takes charge of the processing, and if the other processor is assigned the processing, the first processor communicates with the port unit, transfers the request from the first host processor unit via the port unit to a host processor unit which has the other processor so that the processing to meet the request is carried out at the other processor.