Autonomous Takeover Destination Changing Method in a Failover

A control method in a computer system including:

• a plurality of computers including a first computer, a second computer, and a third computer;
• and
• a storage device coupled to the plurality of computers via a network,
• the first computer including a first interface coupled to the network, a first processor coupled to the first interface, and a first memory coupled to the first processor,
• the second computer including a second interface coupled to the network, a second processor coupled to the second interface, and a second memory coupled to the second processor,
• the third computer including a third interface coupled to the network, a third processor coupled to the third interface, and a third memory coupled to the third processor,
• the method comprising the steps of:
• executing, by the first computer, upon reception of an access request to a storage area of the storage device from a client computer coupled to the plurality of computers, the requested access;
• transmitting, by the first computer, a response to the access request to the client computer;
• judging, by the second computer, whether a failure has occurred in the first computer;
• obtaining, by the second computer, load information of the second computer;
• obtaining, by the second computer, load information of the third computer from the third computer;
• judging, by the second computer, whether the obtained load information satisfies a predetermined condition;
• transmitting, by the second computer, a change request to the third computer when the obtained load information satisfies the predetermined condition;
• and
• judging, by the third computer, whether a failure has occurred in the first computer when the change request is received from the second computer.

A computer system, comprising:

• a plurality of computers including a first computer, a second computer, a third computer, and a fourth computer;
• and
• a storage device coupled to the plurality of computers via a network,
• the first computer including a first interface coupled to the network, a first processor coupled to the first interface, and a first memory coupled to the first processor,
• the second computer including a second interface coupled to the network, a second processor coupled to the second interface, and a second memory coupled to the second processor,
• the third computer including a third interface coupled to the network, a third processor coupled to the third interface, and a third memory coupled to the third processor,
• the fourth computer including a fourth interface coupled to the network, a fourth processor coupled to the fourth interface, and a fourth memory coupled to the fourth processor, wherein:
• the first computer is configured to:
• provide a first service of executing, upon reception of an access request to a storage area of the storage device from a first user of a client computer coupled to the plurality of computers, the requested access, and transmitting to the client computer a response to the access request;
• and
• transmit, upon reception of a first failure monitor request to the first computer providing the first service from the second computer, a response to the first failure monitor request to the second computer;
• the second computer is configured to:
• judge that a failure has occurred in the first computer when the response to the first failure monitor request cannot be received at a predetermined timing;
• obtain load information of the second computer;
• obtain load information of the third computer and load information of the fourth computer by transmitting a load information acquisition request to the third computer and the fourth computer at a predetermined timing and receiving a response containing the load information from the third computer and the fourth computer;
• compare the load information of the fourth computer with the load information of the third computer;
• compare the load information of the third computer with the load information of the second computer when it is judged that a load of the third computer is smaller than a load of the fourth computer;
• transmit a change request to the third computer when it is judged that the load of the third computer is smaller than a load of the second computer;
• transmit, when it is judged that the load of the third computer is smaller than the load of the fourth computer, priority information containing information for identifying the third computer to the third computer and the fourth computer;
• set, when it is judged that a failure has occurred in the first computer, an address same as an address set as a destination of the access request from the client computer to the second computer;
• execute, upon reception of an access request with the set address as the destination, the requested access;
• and
• transmit a response to the access request to the client computer;
• the third computer is configured to:
• transmit the load information of the third computer to the second computer;
• judge whether a failure has occurred in the first computer when the change request is received from the second computer;
• judge that a failure has occurred in the second computer when the load information acquisition request cannot be received at the predetermined timing;
• and
• judge whether a failure has occurred in the first computer when it is judged that a failure has occurred in the second computer and the last priority information received from the second computer contains the information for identifying the third computer;
• the fourth computer is configured to:
• transmit the load information of the fourth computer to the second computer;
• and
• judge whether a failure has occurred in the first computer when the change request is received from the second computer;
• when the computer system further includes as one of the plurality of computers a fifth computer having a fifth interface coupled to the network, a fifth processor coupled to the fifth interface, and a fifth memory coupled to the fifth processor, the fifth computer is configured to:
• transmit load information of the fifth computer to the second computer;
• and
• judge whether a failure has occurred in the first computer when the change request is received from the second computer;
• when one of the plurality of computers receives an instruction to provide a second service that is provided by responding to the access request made with respect to a second storage area of the storage device by a second user, the one of the plurality of computers that has received the instruction is configured to:
• transmit a second failure monitor request to at least one of the plurality of computers providing the second service;
• obtain load information of at least one computer among the plurality of computers;
• transmit, when a response to the second failure monitor request cannot be received at a predetermined timing, the change request to a computer having the smallest load among the at least one computer;
• and
• provide the second service;
• the load information of each of the plurality of computers contains a value indicating a degree of load of each of the plurality of computers;
• and
• the value indicating the degree of load of each of the plurality of computers includes at least one of a usage ratio of the processor included in each of the plurality of computers, a usage ratio of the memory included in each of the plurality of computers, a usage ratio of the network used by each of the plurality of computers, the number of times each of the plurality of computers accesses the storage device, and the number of processes operated in each of the plurality of computers.