Sparing system and method to accommodate equipment failures in critical systems

• US 6,618,819 B1
• Filed: 12/23/1999
• Issued: 09/09/2003
• Est. Priority Date: 12/23/1999
• Status: Expired due to Fees

• Current Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Dysari, Keith C., Waines, Gregory A., Adamovits, Peter J.
• Primary Examiner(s): Beausoliel, Robert
• Assistant Examiner(s): DUNCAN, MARC M
• Application Number:
  US09/471,240
• Time in Patent Office: 1,356 Days
• Field of Search: 714/13, 714/15, 714/4, 714/23, 714/24
• US Class Current: 714/13
• CPC Class Codes: G06F 11/2023 Failover techniques
• CPC Class Codes: G06F 11/2028 eliminating a faulty processor or activating a spare
• CPC Class Codes: G06F 11/2048 where the redundant components share neither address space nor persistent storage
• CPC Class Codes: G06F 11/2097 maintaining the standby controller/processing unit updated initialisation or re-synchronisation thereof G06F11/1658 and subgroups

Abstract

A sparing system and method of accommodating failure of equipment in critical systems comprises, in one embodiment, 1:n sparing where an equipment spare is provided for every n pieces of equipment in the system. The spare equipment includes journal memory wherein an image of the operating system, applications and state of each piece of equipment being spared for can be maintained. The image information is updated at appropriate intervals when the equipment is operating without a failure and, in the event of a piece of equipment failing, the spare equipment loads the state of failed equipment from the corresponding image and commences executing the software in the corresponding image, thus resuming performance of the activities of the failed equipment. In a second embodiment, m:n sparing is provided wherein m pieces of spare equipment are provided for n pieces of equipment to accommodate m failures of the equipment.

Claims

1. A sparing method of accommodating equipment failures in a critical system comprising n pieces of equipment and at least one spare piece of equipment for said n pieces of equipment, comprising the steps of:

(i) loading software onto each of said n pieces of equipment;

(ii) commencing execution of said loaded software with said respective piece of equipment;

(iii) transferring an image of information on each of said n pieces of equipment to a memory on said at least one spare piece of equipment when commencing the execution, said information including said loaded software and a hardware state;

(iv) detecting a failure of one of said n pieces of equipment;

(v) causing said at least one spare piece of equipment to replace said detected one piece of equipment by commencing execution of said image corresponding to said detected one piece of equipment, which is stored in the memory, to employ said at least one spare piece of equipment in place of said detected one piece of equipment.

2. The method of claim 1 further comprising the step of, after step (iii), at each of said n pieces of equipment, at selected intervals, transferring to said memory on said at least one spare piece of equipment information to update said image stored in the memory.

3. The method of claim 2 wherein said selected interval corresponds to a selected number of clock cycles on said pieces of equipment.

4. The method of claim 2 wherein said selected interval corresponds to the occurrence of one or more selected events occurring in a respective piece of equipment.

5. The method of claim 1 wherein at least two pieces of spare equipment is provided and, in step (iii) said image is transferred to a memory on each of said at least two spare pieces of equipment, and in step (v) one of said two or more spare pieces of equipment is selected to replace said detected one piece of equipment by commencing execution of said image corresponding to said detected one piece of equipment to employ said at least one spare piece of equipment in place of said detected one piece of equipment, and wherein step (iii) continues to be performed to transfer said images to each remaining one of said at least two spare pieces of equipment.

6. The method of claim 1 wherein said critical equipment is a data and/or telecommunications switch, said pieces of equipment are network interface processors and said state information includes connection state information.

7. The method of claim 2 wherein said critical equipment is a data and/or telecommunications switch, said pieces of equipment are network interface processors and said state information includes connection state information.

8. A sparing system to accommodate equipment failures in a critical system comprising:

n pieces of equipment, each of equipment including a memory to maintain software to be executed by said piece of equipment and state information for said piece of equipment, said state information including a hardware state;

at least one spare piece of equipment including a journal memory to store an image of said software and said state information maintained in said memory of each of said n pieces of equipment;

a communication path between each of said n pieces of equipment and said at least one piece of equipment to allow transfer of the image of each said piece of equipment to said journal memory when each said piece of equipment commences execution of the software, each of said n pieces of equipment operable to transfer the image maintained in a corresponding memory to said journal memory;

wherein upon determination that one of said n pieces of equipment has experienced a failure, said at least one spare piece of equipment loads said image corresponding to said one piece of equipment and operates to execute said image to replace said one piece of equipment.

9. The sparing system of claim 8 wherein said images further comprise state information for each said respective piece of equipment.

10. The sparing system of claim 8 wherein each of said n pieces of equipment updates said corresponding image in said journal memory of said at least one spare piece of equipment at preselected intervals.

11. The sparing system of claim 8 comprising at least two spare pieces of equipment each of which is operable to store said image of each of said n pieces of equipment and wherein upon determination that one of said n pieces of equipment has experienced a failure, a selected one of said at least two spare pieces of equipment loads said image corresponding to said one piece of equipment and operates to execute said image to replace said one piece of equipment and each remaining one of said at least two spare pieces of equipment continues to store said images and can operate to substitute for a subsequent failed piece of equipment.