Storage apparatus and method of controlling the same

A storage apparatus comprising:

• a controller that receives a data input/output request transmitted from an information apparatus communicatively coupled to the controller, and transmits an I/O request to a storage drive in response to the data input/output request;
• and
• an expander coupled to the controller via a communication path and receives the I/O request transmitted from the controller and transmits the I/O request to the storage drive, wherein the controller includes:
• a communication rate table in which each piece of information indicating a communication rate is stored in association with identification information of the piece of information;
• a controller identification information storage unit that stores controller identification information associated with a maximum communication rate of the controller;
• a controller communication rate setting unit that sets a communication rate for the expander upon detecting that coupling to the expander via the communication path has been established, by transmitting and receiving test data to and from the expander while changing from a predetermined rate a communication rate in the transmission and reception of the test data;
• and
• a controller set value storage unit that stores a set value of the communication rate between the controller and the expander,
• the expander includes:
• an expander identification information storage unit that stores expander identification information associated with a maximum communication rate of the expander;
• and
• an expander identification information transmission unit that transmits the expander identification information stored in the expander identification information storage unit to the controller, upon detecting that coupling to the controller via the communication path has been established, and
• the controller includes:
• an expander identification information receiving unit that receives the expander identification information transmitted from the expander upon detecting that the coupling to the expander via the communication path has been established;
• a controller maximum communication rate identifying unit that identifies the maximum communication rate of the controller on the basis of the piece of information indicating the communication rate stored in the communication rate table in association with the controller identification information;
• an expander maximum communication rate identifying unit that identifies the maximum communication rate of the expander on the basis of the piece of information indicating the communication rate stored in the communication rate table in association with the expander identification information;
• a first expected value calculation unit that obtains a lower one of the maximum communication rate of the controller and the maximum communication rate of the expander as an expected value of the communication rate between the controller and the expander;
• a first communication rate comparison unit that compares the expected value of the communication rate between the controller and the expander with the set value of the communication rate between the controller and the expander;
• and
• a first comparison result storage unit that stores the comparison result obtained by the first communication rate comparison unit.