Apparatus and method for transmitting frames via a switch in a storage area network

• US 6,775,230 B1
• Filed: 07/18/2000
• Issued: 08/10/2004
• Est. Priority Date: 07/18/2000
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Watanabe, Naoki, Yamagami, Kenji
• Primary Examiner(s): Rao, Seema S.
• Assistant Examiner(s): Scheibel, Robert C
• Application Number:
  US09/618,318
• Time in Patent Office: 1,484 Days
• Field of Search: 370/216, 370/217, 370/218, 370/225, 370/228, 709/250, 709/238, 709/239, 714/1-4, 714/43
• US Class Current: 370/228
• CPC Class Codes: H04L 41/0836 to enhance reliability, e.g. reduce downtime
• CPC Class Codes: H04L 41/0879 Manual configuration through operator
• CPC Class Codes: H04L 41/0886 Fully automatic configuration
• CPC Class Codes: H04L 49/357 Fibre channel switches
• CPC Class Codes: H04L 49/555 Error detection
• CPC Class Codes: H04L 49/557 Error correction, e.g. fault recovery or fault tolerance

Abstract

A method and apparatus is provided to determine a path from a plurality of predetermined paths between a server system and a storage system in a Storage Area Network by a Fiber Channel Fabric, including one or more Fiber Channel switches. One embodiment, provides a method for selecting a path from a plurality of pre-determined paths between a computer system and a storage system in a Storage Area Network, where the computer system and the storage system are connected together by one or more Fiber Channel switches. The method includes, establishing a first path from the plurality of pre-determined paths between the computer system and the storage system. Next, a status of the first path is determined by the Fiber Channel switch or switches; and a second path from the plurality of pre-determined paths is selected based on the status of the first path. The selection by the Fiber Channel switch is independent of the computer system. The status could be, for example, a first path failure, such as a loss of reliable communications on a link of the first path, or a first path usage above a threshold.

Claims

1. A method for transmitting frames between a computer system and a storage system in a Storage Area Network, wherein the computer system and the storage system are coupled together by a switch, wherein at least a first port with a first port ID of the switch is coupled to the computer system, wherein a plurality of ports of the switch are coupled to the storage system, the method comprising:

mapping a logical volume presented by the storage subsystem to at least a second port with a second port ID and a third port with a third port ID of the ports, wherein the logical volume is accessed by the computer system;

establishing, at the switch, a first path between the first port and the second port and a second path between the first port and the third port;

selecting the first path to send a frame from the computer system;

receiving, at the switch, a first frame including the second port ID from the computer system;

sending the first frame including the second port ID to the storage system via the first path;

receiving, at the storage system, the first frame including the second port ID from the second port;

determining a status of the first path by the switch; and

switching from the first path to the second path based on the status;

receiving, at the switch, a second frame including the second port ID from the computer system;

sending the second frame including the second port ID to the storage system via the second path;

accepting, at the storage system, the second frame including the second port ID received from the third port.

2. The method of claim 1 wherein the status comprises a first path failure.

3. The method of claim 2 wherein the first path failure comprises a loss of reliable communications on a on a link of the first path.

4. The method of claim 1 wherein the status comprises a first path usage above a threshold.

5. The method of claim 1 wherein the switch is a Fibre Channel switch.

6. The method of claim 1 wherein the first path and the second path belong to a same path group.

11. The computer program of claim 4, further comprising:

code for selecting the first path for sending a frame from the computer system to the storage system; and

code for selecting the second pat for sending a frame from the computer system to the storage system if the first path is determined to be in an unfavorable state.

7. A method for transmitting frames from a computer system to a storage system via a switch provided in a network, the switch having at least first, second and third ports, the method comprising:

mapping a logical volume defined in the storage subsystem to at least the first port having first port identification information and a second port having second port identification information, the computer system being coupled to at least the third port having third port identification information;

establishing a first path between the first port and the third port and a second path between the second port and the third port;

receiving, at the switch, a first frame including the first port identification information from the computer system;

sending the first frame from the switch to the storage system via the first path, wherein the storage system receives the first frame via the first port, the first frame being processed within the storage system;

receiving, at the switch, a second frame including the first port identification information from the computer system;

sending the second frame including the fist port identification to the storage system via the second path, wherein the storage system receives the second frame via the second port the second frame being processed within the'"'"'storage system.

8. The method of claim 7, further comprising:

selecting the first path for sending a frame from the computer system to the storage system; and

selecting the second path for sending a frame from the computer system to the storage system if the first path is determined to be in an unfavorable state.

9. The method of claim 7, wherein the second frame received by the storage system via the second port does not include the second port identification information.

10. A computer readable medium including a computer program for transmitting frames from a computer system to a storage system via a switch provided in a network, the switch having at least first, second and third ports, wherein a logical volume defined in the storage subsystem is mapped to at least the first port having first port identification information and a second port having second port identification information, the computer system being coupled to at least the third port having third port identification information, the computer program comprising:

code for establishing a first path between the first port and the third port and a second path between the second port and the third port;

code for receiving, at the switch, a first frame including the first port identification information from the computer system;

code for sending the first frame from the switch to the storage system via the first path, wherein the storage system receives the first frame via the first port, so that the first frame may be processed within the storage system;

code for receiving, at the switch, a second frame including the first port identification information from the computer system;

code for sending the second frame including the first port identification to the storage system via the second path, wherein the storage system receives the second frame via the second port, so that the second frame may be processed within the storage system.