Storage system having sas as its backend communication standard

A method of managing physical ports of a storage system which has

• a plurality of storage devices;
• first and second controllers coupled to a host;
• a first communication path, which is coupled to the first controller and the plurality of storage devices, and which is a path for communications according to Serial Attached SCSI (SAS);
• and
• a second communication path, which is coupled to the second controller and the plurality of storage devices, and which is a path for communications according to SAS,
• wherein the first communication path comprises a plurality of first-expanders that are coupled in series, and a top first-expander of the plurality of first-expanders is coupled to the first controller,
• wherein the second communication path comprises a plurality of second-expanders that are coupled in series, and a top second-expander of the plurality of second-expanders is coupled to the second controller,
• wherein each of the first-expanders comprises a plurality of first phys (physical ports), and the plurality of first phys include a first phy (physical port) coupled to one of the storage device which is not coupled to any of the other of the plurality of first phys, and another first phy coupled to a next first-expander of the plurality of first-expanders,
• wherein each of the plurality of first-expanders and the plurality of second-expanders includes routing control information that is used in routing,
• wherein the routing control information can include SAS address information denoting the SAS address of a storage device indirectly coupled to each phy, and status information denoting that the respective storage device is either valid or invalid,
• the method comprising the steps of:
• (A) detecting a link-down for a target storage device, which is the storage device that is directly coupled to a certain first phy of a certain first-expander in the first communication path,
• (B) determining whether or not the link-down satisfies a prescribed condition,
• (C) issuing, in a case where the result of the determination of (B) is negative, a second information setting command which includes information denoting that the target storage device is invalid and phy information denoting the first phys indirectly coupled to the target storage device, to each first-expander that exists in the initial stage further forward than the certain first-expander, so that each of the first-expanders having received the second information setting command, can set, in the routing control information, the status information denoting that the target storage device is invalid for the phy identified from the phy information inside the second information setting command.