Patent ID: 8543762

Claim:
A computer system, comprising: a plurality of SAS target devices constituting targets that follow the SAS protocol; a SAS initiator device constituting an initiator that follows the SAS protocol, which is connected to a host computer that accesses data stored in the plurality of SAS target devices; and a switch section that is connected to at least one SAS target device by means of a physical link which is physical wiring, and that is connected to the SAS initiator device by means of a wide link constituted by a plurality physical links, wherein the switch section includes one or a plurality of SAS expander devices, each SAS expander device including at least one wide port, which is (i) coupled to a plurality of physical links, (ii) includes a plurality of physical communication ports each identified by a respective physical communication port ID, and (iii) has a respective SAS address allocated thereto, and a physical-link allocation control section, and, when the switch section is constituted by a plurality of SAS expander devices, the plurality of SAS expander devices are cascade -connected with the SAS expander device connected to the SAS initiator device in the leading position and each SAS expander device is connected to one another by means of the wide link, the computer system further comprises a physical-link allocation control section that controls allocation to each of the plurality of SAS target devices in the plurality of physical links constituting the wide link, wherein an I/O request that the SAS initiator device received from the host computer is sent to the SAS target device via the switch section, wherein an I/O request is sent via a physical link allocated to the SAS target device and cannot pass a physical link that is not allocated to the SAS target device, wherein each SAS expander device is configured, when an initiator device or a target device issues a predetermined frame for establishing a connection via an open address frame, to refer to expander tables using a transmitting target SAS address as a destination written in the open address frame, and to identify an enabled physical link in the wide port, and wherein each SAS expander device is configured to select a physical link having not established a connection among the enabled physical links, and to establish a connection as for the selected physical link.