1. A storage system, comprising: a base chassis including a first storage device, a controller for responding to an I/O request from a host system and controlling the input and output of data to and from said first storage device, a resource management processor for managing a chassis resource in the said basic chassis, and a system drive for storing a revision of main firmware of said resource management processor; and one or more expanded chassis each including a second storage device, a first Fiber Channel/Serial Advanced Technology Attachment (FC/SATA) converter connected to said second storage device, and a second FC/SATA converter connected to said second storage device, wherein said resource management processor monitors the temperature of said controller, wherein said controller performs a first comparative determination for comparing a revision of the main firmware installed in said resource management processor and the revision of the main firmware of said resource management processor stored in said system drive and, upon determining that the revision of the main firmware installed in said resource management processor is older than the revision of the main firmware of said resource management processor stored in said system drive, renews the revision of the main firmware installed in said resource management processor to the revision of the main firmware of said resource management processor stored in said system drive, wherein said controller performs a second comparative determination for comparing a revision of main firmware installed in said first FC/SATA converter and a revision of main firmware of said first FC/SATA converter stored in said system drive, and wherein said controller, upon determining that the revision of the main firmware installed in said first FC/SATA converter is older than the revision of the main firmware of said first FC/SATA stored in said system drive, directs blocking of said first FC/SATA converter, switches an allocation destination of said second storage device from said first FC/SATA converter to said second FC/SATA converter, switches from a first connection path with said first FC/SATA converter to a second connection path with said second FC/SATA converter, renews the revision of the main firmware installed in said first FC/SATA converter to the revision of the main firmware of said first FC/SATA converter stored in said system drive, switches the allocation destination of said second storage device back to said first FC/SATA converter, and switches back from the second connection path with said second FC/SATA converter to the first connection path with said first FC/SATA converter.