Patent ID: 8667337

Claim:
A storage apparatus comprising: a first controller having a processor, a memory, and a network I/F that receives a data input/output request from an external apparatus; a second controller having a processor, a memory, and a network I/F that receives a data input/output request from the external apparatus; a plurality of first expanders configuring a first system by being communicatively coupled to a storage drive, having a plurality of communication ports, and being in cascade connection with the first controller through the communication ports; a plurality of second expanders configuring a second system by being communicatively coupled to another storage drive, having a plurality of communication ports, and being in cascade connection with the second controller through the communication ports, wherein the first controller accesses the storage drive through at least one of the first expanders in response to the data input/output request, the second controller accesses the other storage drive through at least one of the second expanders in response to the data input/output request, the first controller transmits an instruction to execute a diagnosis on the communication ports to the first expanders, the first expanders, upon receiving the instruction, diagnose the communication ports thereof, and the first controller stores a concurrently-executable maximum number being a maximum number of the communication ports concurrently diagnosable in the first system, and causes the first expanders to execute the diagnosis on the communication ports in the first system by repeatedly performing a process of selecting a number of the communication ports not exceeding the concurrently-executable maximum number and a process of transmitting an instruction to perform the diagnosis on the selected communication ports to the first expanders.