Patent ID: 8819319

Claim:
A computer system formed so that a server chassis having at least one server and an IO slot expansion unit loaded with a PCIe switch are connected to each other by a PCIe cable, wherein: the server has an arithmetic portion, a storage portion, and an HBA identifier update control portion; the IO slot expansion unit has the PCIe switch, an IO slot expansion unit controller connected to the PCIe switch, and a plurality of PCI card slots connected to the PCIe switch; a first PCI cards having a first HBA and a first HBA port is mounted in a first PCI card slot, the first PCI card slot is identified by a first PCI card slot identifier, and the first HBA port is assigned a first port number; the first HBA has a first identifier area which is arranged to hold a first allocated identifier by which the first HBA port is identified; the PCIe switch has a PCIe switch register; the IO slot expansion unit controller has a PCIe switch register update control portion and an identifier allocation table for managing the first PCI card slot identifier of the first PCI card slot, the first port number of the first HBA port on the first PCI card, and the first allocated identifier corresponding to the first PCI card slot identifier; the PCIe switch register update control portion is arranged to copy the identifier allocation table of the IO slot expansion unit controller to an identifier storage area of the PCIe switch register in the PCIe switch in response to powering on the IO slot expansion unit; and the HBA identifier update control portion is arranged to: acquire the identifier allocation table copied to the identifier storage area of the PCIe switch register in the PCIe switch through the PCIe cable in response to powering on the server; store the acquired identifier allocation table in the storage portion of the server; refer to the first allocated identifier corresponding to the first PCI card slot identifier and the first port number of the first HBA port on the first PCI card in the identifier allocation table stored in the storage portion; and in a case where the first PCI card is replaced with a second PCI card having a second identifier area and a second HBA port in the first PCI card slot connected to the PCIe switch, update an allocated identifier of the second HBA port, which is assigned the first port number, in the second identifier area to the first allocated identifier.