US Patent 7280485 Method and apparatus for diagnosing FC-AL system link

Upon detection of a fault of a loop or any of disk apparatuses 30, 40, and 50, an FC-AL control unit 15 notifies an MPU11 of contents of the fault. The MPU11 records a fault history for each disk apparatus in a memory circuit 12 and also sets an order in which the disk apparatuses 30, 40, and 50 are to be disconnected, based on the fault histories. If the link fault occurs, the disk apparatuses 30, 40, and 50 are disconnected from the loop in thus set disconnecting order. If the link failure occurs on the port A side loop 1, a disk adapter 10 supplies a port bypassing-related instruction to its counterpart disk adapter 20 to thereby control bypassing/bypassing releasing on the port A side through the port B side loop 2.