Storage subsystem and load distribution method for executing data processing using normal resources even if an abnormality occurs in part of the data processing resources that intermediate data processing between a host computer and a storage device

Abstract

A storage subsystem coupled to a host computer is described. The storage subsystem includes storage devices and first and second storage apparatuses that control data transfer between the host computer and the storage devices. The first storage apparatus includes a first controller coupled to the host computer via a first host communication control unit and to the storage devices via a first storage device communication control unit. The second storage apparatus includes a second controller coupled to the host computer via a second host communication control unit and to the storage devices via a second storage device communication control unit. At least one of the controllers monitors a status of the first host communication control unit and the storage device communication control units, and, if the status of the first storage device communication unit indicates failure, switch communication paths for transferring data from the host computer to the storage devices.