System and method to failover storage area network targets from one interface to another

• US 7,127,633 B1
• Filed: 06/28/2002
• Issued: 10/24/2006
• Est. Priority Date: 11/15/2001
• Status: Active Grant

• Current Assignee: Xiotech Corporation
• Original Assignee: Xiotech Corporation
• Inventors: Pittelkow, Michael Henry, Olson, Mark David
• Primary Examiner(s): Beausoliel, Robert
• Assistant Examiner(s): Wilson, Yolanda L.
• Application Number:
  US10/184,058
• Time in Patent Office: 1,579 Days
• Field of Search: 714/4, 714/6
• US Class Current: 714/4.4
• CPC Class Codes: G06F 11/2092 Techniques of failing over between control units

Abstract

A fiber channel storage area network (SAN) provides virtualized storage space for a number of servers to a number of virtual disks implemented on various virtual redundant array of inexpensive disks (RAID) devices striped across a plurality of physical disk drives. The SAN includes plural controllers and communication paths to allow for fail-safe and fail-over operation. The plural controllers can be loosely-coupled to provide n-way redundancy and have more than one independent channel for communicating with one another. In the event of a failure involving a controller or controller interface, the virtual disks that are accessed via the affected interfaces are re-mapped to another interface in order to continue to provide high data availability. In particular, those targets, or virtual disks, which are owned by a failed device (e.g., interface or controller) are identified and their ownership information within the SAN configuration tables is revised to reflect one or more alternative devices which act as back-up devices.

Claims

1. A storage area network comprising:

a plurality of loosely coupled storage controllers arranged in a redundant configuration;

respective sets of front-end interfaces, each said set associated with one of the storage controllers and each front-end interface in a respective set providing access to one or more associated targets, to one of a plurality of connected servers;

wherein the storage controllers are arranged to include only one master controller and one or more slave controllers and

a configuration and control board in each storage controller configured to move any targets associated with a respective front-end interface to one or more other front-end interfaces, wherein only the configuration and control board in the master controller is permitted to move a target from one front-end interface to another by changing configuration information relating to the storage area network maintained by the configuration and control board in the master controller.

2. The storage area network according to claim 1, wherein each configuration and control board is further configured to move any targets in response to a failure occurring on the respective front-end interface.

3. The storage area network according to claim 1, wherein each of the front-end interfaces is a fibre channel host adapter board.

4. The storage area network according to claim 1, wherein each of the front-end interfaces connects to all of the servers.

5. The storage area network according to claim 1, wherein the configuration and control board on each of the storage controllers maintains a respective indication of the relationship between each of the front-end interfaces and each of the targets, and moving a particular target associated with a first interface to be associated with a second interface includes changing an indicated relationship for the particular target from the first interface to the second interface.

6. The storage area network according to claim 1, wherein each of the targets is a virtual disk that can be accessed by one or more of the servers.

7. The storage area network according to claim 1, wherein the configuration and control board on the master controller is configured to propagate any changed configuration information to each of the slave controllers.

8. The storage area network according to claim 1, wherein the configuration information relating to the storage area network includes a table that indicates a relationship between each of the targets and each of the front-end interfaces, and changing of the configuration information includes modifying the relationships of those targets being moved.

9. The storage area network according to claim 1, further comprising a resource management application permitted to execute only on the configuration and control board in the master controller and configured to determine to which of the front-end interfaces a target will be moved.

10. A method, in a storage area network comprising plural loosely-coupled redundant controllers, for mapping a target from a first front-end interface to a second front-end interface, comprising the steps of:

identifying an operational failure that affects a first front-end interface on a first controller;

identifying one or more targets owned by the first front-end interface, wherein each target is a virtual disk presented to a server via the storage area network;

modifying ownership information of the identified one or more targets such that each of the one or more targets are no longer owned by the first front-end interface but are owned by a respective second front-end interface;

analyzing the input/output load on a plurality of front-end interfaces associated with the redundant storage controllers; and

determining each respective second front-end interface based on the analyzed load; and

updating respective configuration information used by each of the redundant controllers to reflect the modified ownership information of the identified one or more targets.

11. The method according to claim 10, wherein each of the respective second front-end interfaces is one and the same interface.

12. The method according to claim 10, further comprising the steps of:

identifying a specific controller associated with the first front-end interface, said specific controller having a set of interfaces other than the first front-end interface; and

determining each respective second front-end interface from among the set of interfaces.

13. The method according to claim 10, further comprising the steps of:

arranging the redundant controllers to include only one master controller and one or more slave controllers;

maintaining configuration information for the storage area network on each redundant controller, wherein the configuration information includes an indication of ownership of a particular target by a particular front-end interface;

permitting the step of modifying the indication of ownership to be performed only by the master controller; and

propagating the modified indication of ownership to each of the slave controllers.