Methods and apparatus for coordinating shared multiple raid controller access to common storage devices

• US 6,457,098 B1
• Filed: 02/08/2000
• Issued: 09/24/2002
• Est. Priority Date: 12/23/1998
• Status: Expired due to Term

• Current Assignee: NetApp, Inc.
• Original Assignee: LSI Logic Corporation (Broadcom, Inc.)
• Inventors: Fredin, Gerald J., DeKoning, Rodney A.
• Primary Examiner(s): Nguyen, Hiep T.
• Application Number:
  US09/499,926
• Time in Patent Office: 959 Days
• Field of Search: 711/114, 711/152, 711/150, 714/6
• US Class Current: 711/114
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0635 by changing the path, e.g. traffic rerouting, path reconfiguration
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD

Abstract

Methods and associated apparatus for performing concurrent I/O operations on a common shared subset of disk drives (LUNs) by a plurality of RAID controllers. The methods of the present invention are operable in all of a plurality of RAID controllers to coordinate concurrent access to a shared set of disk drives. The plurality of RAID controllers operable enhance the performance of a RAID subsystem by better utilizing available processing power among the plurality of RAID controllers. Each of a plurality of RAID controllers may actively process different I/O requests on a common shared subset of disk drives. One of the plurality of controllers is designated as primary with respect to a particular shared subset of disk drives. The plurality of RAID controllers then exchange messages over a communication medium to coordinate concurrent access to the shared subset of disk drives through the primary controller.

Claims

1. A RAID storage system comprising:

a plurality of disk drives forming a common shared LUN;

a communication medium; and

a plurality of RAID storage control modules connected to said common shared LUN including;

a primary RAID storage control module coupled to said disk drives and coupled to said communication medium; and

a

a plurality of secondary RAID storage control modules coupled to said disk drives and coupled to said communication medium,

wherein access control messages are exchanged between said primary RAID storage control module and said plurality of secondary RAID)storage control modules via said communication medium to coordinate temporary exclusive access by one of said plurality of storage RAID control modules to identified stripes within said plurality of disk drives.

2. The system of claim 1 wherein each of said plurality of secondary RAID storage control modules includes:

a request generator to generate an exclusive access request message;

a request transmitter coupled to said request generator to transmit said exclusive access request message to said primary RAID storage control module; and

a secondary RAID storage control module access coordinator coupled to said request transmitter to await receipt by said secondary RAID storage control module of an exclusive access grant message from said primary RAID storage control module granting exclusive access to said identified stripes.

3. The system of claim 2 wherein said primary RAID storage control module includes:

a request receiver to receive said exclusive access request message;

a primary RAID storage control module access coordinator coupled to said request receiver to await availability of exclusive access to said identified stripes in response to receipt of said exclusive access request message;

a response generator coupled to said access coordinator to generate said exclusive access grant message in response to availability of exclusive access to said identified stripes; and

a grant transmitter to transmit said exclusive access grant message to said plurality of secondary RAID storage control modules.

4. The system of claim 3 wherein said primary RAID storage control module access coordinator includes:

a plurality of semaphores;

a semaphore tester to determine that none of said plurality of semaphores is associated with said identified stripes;

a semaphore association directory for associating one semaphore of said plurality of semaphores with said identified stripes in response to the determination that none of said plurality of semaphores is associated with said identified stripes; and

a semaphore locker to lock said one semaphore associated with said identified stripes.

5. The system of claim 4 wherein said secondary RAID storage control module access coordinator further includes:

a release generator to generate an exclusive access release message; and

a release transmitter to transmit said exclusive access release message to said primary RAID storage control module.

6. The system of claim 5 wherein said primary RAID storage control module access coordinator further includes:

a release receiver to receive said exclusive access release message wherein said release message includes indicia of the locked semaphore associated with said identified stripes;

a semaphore locator to locate the locked semaphore in said semaphore association directory; and

a semaphore unlocker to unlock the locked semaphore to thereby releasing exclusive access to said identified stripes in response to receipt of said exclusive access release message.

7. A RAID storage system comprising:

a set of storage devices forming a commonly shared LUN;

a plurality of RAID storage control modules commonly coupled to said commonly shared LUN wherein one of said plurality of RAID storage control modules is designated as a primary RAID storage control module, wherein said plurality of RAID storage control modules includes at least three RAID storage controllers;

means, within said plurality of RAID storage control modules, for receiving a plurality of I/O requests from attached host computer systems; and

means for processing each of said plurality of I/O requests substantially in parallel within distinct RAID storage control modules of said plurality of RAID storage control modules wherein said means for processing includes means for exchanging exclusive access messages between said primary RAID storage control module and others of said plurality of RAID storage control modules.

8. The system of claim 7 wherein said means for processing further includes:

means for coordinating temporary exclusive access to said common shared set of storage devices by said distinct control modules.

9. The system of claim 8:

wherein said exclusive access messages include exclusive access request messages directed from said others of said plurality of RAID storage control modules to said primary RAID storage control module,

wherein said exclusive access messages include exclusive access grant messages directed from said primary RAID storage control module to said others of said plurality of RAID storage control modules, and

wherein said exclusive access messages include exclusive access release messages directed from said others of said plurality of RAID storage control modules to said primary RAID storage control module.

10. A RAID storage controller attachable to a commonly shared LUN of a plurality of disk drives in a RAID storage subsystem, said storage controller comprising:

means for receiving I/O requests from host systems coupled to said RAID storage controller;

means, responsive to receipt of an I/O request, for coordinating access to portions of said plurality of disk drives by said storage controller with access to said plurality of disk drives by other RAID storage controllers to assure temporary mutual exclusivity between said RAID storage controller and said other RAID storage controllers;

inter-controller communication interface means for coupling said RAID storage controller to said other RAID storage controllers,

wherein one of said other RAID storage controllers is designated as a primary RAID storage controller and wherein the means for coordinating includes;

means for exchanging exclusive access messages via said inter-controller communication interface means between said RAID storage controller and said primary RAID storage controller to assure temporary mutually exclusive access to said portions of said plurality of disk drives by said RAID storage controller.

11. The system of claim 10:

wherein said exclusive access messages include exclusive access request messages directed from said RAID storage controller to said primary RAID storage controller,

wherein said exclusive access messages include exclusive access grant messages directed from said primary RAID storage controller to said RAID storage controller, and

wherein said exclusive access messages include exclusive access release messages directed from said RAID storage controller and said other RAID storage controllers to said primary RAID storage control module.