Patent ID: 8312234

Claim:
A storage system comprising: a first storage module that includes a first controller and a first physical storage device; and a second storage module that includes a second controller and a second physical storage device, wherein a host computer that sends an I/O command for data I/O is coupled to at least the first storage module of the first and second storage modules, wherein the first controller includes a first storage resource that stores first management information, which is information that is used to control a data I/O, a first processor that controls the data I/O based on the first management information, a first front-end interface, and a first back-end interface, wherein the second controller includes a second storage resource that stores second management information, which is information that is used to control a data I/O, a second processor that controls the data I/O based on the second management information, a second front-end interface, and a second back-end interface, wherein there are a loose coupling and a tight coupling of the first and second storage modules, wherein the loose coupling is a coupling in which the first and second front-end interfaces are coupled together by way of a front-end path, and the first processor is not able to access the second storage resource, wherein the tight coupling is a coupling in which the first and second back-end interfaces are coupled together by way of a back-end path, and the first processor is able to access the second storage resource, wherein the following processing flow is carried out so that coupling of the first and second storage modules is switched from the loose coupling to the tight coupling without the first and second storage modules being partitioned into respectively independent storage modules: (A) the first and second back-end interfaces are coupled together by way of the back-end path; and (B) the first processor merges information denoted by the second management information from the second storage resource with the first management information via the back-end path.