Method for providing a fault tolerant network using distributed server processes to remap clustered network resources to other servers during server failure

• US 6,292,905 B1
• Filed: 10/02/1997
• Issued: 09/18/2001
• Est. Priority Date: 05/13/1997
• Status: Expired due to Term

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Pellicer, Thomas J., Wallach, Walter A., Chrabaszcz, Michael, Findlay, Bruce
• Primary Examiner(s): Lee, Thomas
• Assistant Examiner(s): NGUYEN, NGUYEN X
• Application Number:
  US08/942,815
• Time in Patent Office: 1,447 Days
• Field of Search: 714/4, 714/7, 714/11, 714/17, 714/1, 714/3, 714/6, 714/10, 709/239
• US Class Current: 714/4.12
• CPC Class Codes: G06F 11/2033 switching over of hardware resources
• CPC Class Codes: G06F 11/2035 without idle spare hardware
• CPC Class Codes: G06F 11/2046 where the redundant components share persistent storage G06F11/2043 takes precedence
• CPC Class Codes: G06F 11/2097 maintaining the standby controller/processing unit updated initialisation or re-synchronisation thereof G06F11/1658 and subgroups
• CPC Class Codes: G06F 9/4411 Configuring for operating with peripheral devices; Loading of device drivers
• CPC Class Codes: H04L 41/0663 Performing the actions predefined by failover planning, e.g. switching to standby network elements
• CPC Class Codes: H04L 41/0816 the condition being an adaptation, e.g. in response to network events
• CPC Class Codes: H04L 41/0836 to enhance reliability, e.g. reduce downtime
• CPC Class Codes: H04L 41/12 Discovery or management of network topologies
• CPC Class Codes: H04L 43/0817 by checking functioning
• CPC Class Codes: H04L 61/45 Network directories; Name-to-address mapping
• CPC Class Codes: H04L 67/1095 Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
• CPC Class Codes: H04L 69/40 for recovering from a failure of a protocol instance or entity, e.g. service redundancy protocols, protocol state redundancy or protocol service redirection management of faults, events, alarms or notifications in data switching networks H04L41/06

Abstract

The method of the current invention provides a fault tolerant access to a network resource. A replicated network directory database operates in conjunction with server resident processes to remap a network resource in the event of a server failure. The records/objects in the replicated database contain for each network resource, a primary and a secondary server affiliation. Initially, all users access a network resource through the server identified in the replicated database as being the primary server for the network resource. When server resident processes detect a failure of the primary server, the replicated database is updated to reflect the failure of the primary server, and to change the affiliation of the network resource from its primary to its backup server. This remapping occurs transparently to whichever user/client is accessing the network resource. As a result of the remapping, all users access the network resource through the server identified in the replicated database as the backup server for the resource. When the server resident processes detect a return to service of the primary server, the replicated database is again updated to reflect the resumed operation of the primary server. This remapping of network resource affiliations also occurs transparently to whichever user/client is accessing the network resource, and returns the resource to its original fault tolerant state.

Claims

1. A method for fault tolerant access to a network resource, on a network with a client workstation and a first and a second server, said method for fault tolerant access comprising the acts of:

selecting a first server to provide communications between a client workstation and a network resource;

detecting a failure of the first server, comprising the acts of;

monitoring across a common bus, at a second server, communications between the first server and the network resource across the common bus by noting a continual change in state of the network resource, and

observing a termination in the communications between the first server and the network resource across the common bus by noting a stop in the continual change in state of the network resource; and

routing communications between the client workstation and the network resource via the second server.

2. The method for fault tolerant access to a network resource of claim 1, further comprising the acts of:

identifying in a first record, the primary server for the network resource as the first server;

discovering a recovery of the first server; and

re-routing communications between the client workstation and the network resource via the first server.

3. The method for fault tolerant access to a network resource of claim 2, further comprising

providing a network resource database;

and

replicating the network resource database on the first and the second servers.

4. The method for fault tolerant access to a network resource of claim 2, wherein said act of detecting a recovery of the first server, further includes the acts of:

sending packets intermittently from the second server to the first server; and

re-acquiring acknowledgments from the first server at the second server, the acknowledgments responsive to said sending act and to the recovery of said first server.

5. The method for fault tolerant access to a network resource of claim 1, further comprising:

choosing the first server as the primary server and the second server as the backup server, for the network resource; and

storing in a first field of the first record the primary server for the network resource and sorting in a second field of the first record the backup server for the network resource.

6. The method for fault tolerant access to a network resource of claim 5, wherein said choosing act, includes the act of:

allowing a network administrator to select the primary and the backup server.

7. The method for fault tolerant access to a network resource of claim 5, wherein said act of detecting a failure of the first server, further includes the acts of:

reading the second field in the first record of the network resource database;

determining on the basis of said reading act that the second field identifies the backup server for the network resource as the second server;

activating the monitoring by the second server of the first server, in response to said determining act; and

ascertaining at the second server a failure of the first server.

8. The method for fault tolerant access to a network resource of claim 6, wherein said act of ascertaining at the second server a failure of the first server, further includes the acts of:

sending packets intermittently from the second server to the first server;

receiving acknowledgments from the first server at the second server, the acknowledgments responsive to said sending act; and

noticing a termination in the receipt of acknowledgments from the first server.

9. The method for fault tolerant access to a network resource of claim 5, wherein said act of recognizing the backup server for the network resource, further includes the acts of:

reading the second field in the first record of the network resource database; and

determining that the second field identifies the backup server for the network resource as the second server.

10. A program storage device encoding instructions for:

causing a computer to provide a network resource database, the database including individual records corresponding to network resources, and the network resource database including a first record corresponding to the network resource and the first record identifying a primary server for the network resource as a first server;

causing a computer to select, on the basis of the first record, the first server to provide communications between a client workstation and the network resource;

causing a computer to recognize the backup server for the network resource as the second server;

causing a computer to detect a failure of the first server, including;

causing a computer to monitor across a common bus, at the second server, communications between the first server and the network resource across the common bus by noting a continual change in state of the network resource, and

causing a computer to observe a termination in the communications between the first server and the network resource across the common bus by noting a stop in the continual change in state of the network resource; and

causing a computer to route communications between the client workstation and the network resource via the second server, responsive to said recognizing and detecting acts.

11. The program storage device of claim 10, further comprising instructions for:

causing a computer to identify in the first record, the primary server for the network resource as the first server;

causing a computer to discover a recovery of the first server; and

causing a computer to re-route communications between the client workstation and the network resource via the first server, responsive to said identifying and discovering acts.

12. The program storage device of claim 11, further including instructions for:

causing a computer to replicate a network resource database on the fist and the second server.

13. The program storage device of claim 11, wherein said instructions for causing a computer to detect a recovery of the first server, further includes instructions for:

causing a computer to send packets intermittently from the second server to the first server; and

causing a computer to acquire acknowledgments from the first server at the second server, the acknowledgments responsive to said sending act and to the recovery of the first server.

14. The program storage device of claim 13, further including instructions for:

causing a computer to choose the first server as the primary server and the second server as the backup server, for the network resource; and

causing a computer to store in a first field of the first record the primary server for the network resource and storing in a second field of the first record the backup server for the network resource.

15. The program storage device of claim 14, wherein said instructions for causing a computer to choose, further include:

causing a computer to allow a network administrator to select the primary and the backup server.

16. The program store device of claim 14, wherein said instructions for causing a computer to detect a failure of the first server further include instructions for:

causing a computer to read the second field in the first record of the network resource database;

causing a computer to determine on the basis of said reading act that the second field identifies the backup server for the network resource as the second server;

causing a computer to activate the monitoring by the second server of the first server, in response to said determining act; and

causing a computer to ascertain at the second server a failure of the first server.

17. The program storage device of claim 16, wherein said instructions for causing a computer to ascertain at the second server a failure of the first server, further includes instructions for:

causing a computer to send packets intermittently from the second server to the first server;

causing a computer to receive acknowledgments from the first server at the second server, the acknowledgments responsive to said sending act; and

causing a computer to notice a termination in the receipt of acknowledgments from the first server.

18. The program storage device of claim 14, wherein said instructions for causing a computer to recognize the backup server for the network resource, further include instructions for:

causing a computer to read the second field in the first record of the network resource database; and

causing a computer to determine on the basis of said reading act that the second field identifies the backup server for the network resource as the second server.

19. A method for providing fault tolerant access to a network resource, on a network with a client workstation and a first and a second server and a network resource database, wherein the network resource database includes a first record corresponding to a network resource and the first record includes a first field containing the name of the network resource and a second field containing the host server affiliation of the network resource;

said method for fault tolerant access comprising the acts of;

expanding the network resource database to include a third field for naming the primary server affiliation for the network resource and a fourth field for naming the backup server affiliation for the network resource;

naming the first server in the third field;

selecting, on the basis of the first record, the first server to provide communications between the client workstation and the network resource;

naming the second server in the fourth field;

recognizing, on the basis of the fourth field of the first record, the backup server for the network resource as the second server;

detecting a failure of the first server, including the acts of;

monitoring across a common bus, at the second server, communications between the first server and the network resource across the common bus by noting a continual change in state of the network resource, and

observing a termination in the communications between the first server and the network resource across the common bus by noting a stop in the continual change in state of the network resource; and

routing communications between the client workstation and the network resource via the second server, responsive to said recognizing and detecting acts.

20. The method for fault tolerant access to a network resource of claim 19, further comprising the acts of:

monitoring the server named in the third field;

discovering a recovery of the server named in the third field; and

re-routing communications between the client workstation and the network resource via the first server, responsive to said monitoring and discovering acts.

21. The method for fault tolerant access to a network resource of claim 20, wherein said act of discovering a recovery of the first server, further includes the acts of:

sending packets intermittently from the second server to the first server; and

re-acquiring acknowledgments from the first server at the second server, the acknowledgments responsive to said sending act and to the recovery of said first server.

22. The method for fault tolerant access to a network resource of claim 19, wherein said naming acts, include the acts of:

allowing a network administrator to name the primary server affiliation and the backup server affiliation in the third and fourth fields of the first record of the network resource database.

23. The method for fault tolerant access to a network resource of claim 19, wherein said act of detecting a failure of the first server, further includes the acts of sending

sending packets intermittently from the second server to the first server;

receiving acknowledgments from the first server at the second server, the acknowledgments responsive to said sending act; and

noticing a termination in the receipt of acknowledgments from the first server.

24. A computer usable medium having computer readable program code means embodied therein for causing fault tolerant access to a network resource on a network with a client workstation and a first and second server, and a network resource database, wherein the network resource database includes a first record corresponding to a network resource and the first record includes a first field containing the name of the network resource and a second field containing the host server affiliation of the network resource;

the computer readable program code means in said article of manufacture comprising;

computer readable program code means for causing a computer to expand the network resource database to include a third field for naming the primary server affiliation for the network resource and a fourth field for naming the backup server affiliation for the network resource;

computer readable program code means for causing a computer to name the first server in the third field;

computer readable program code means for causing a computer to select, on the basis of the first record, the first server to provide communications between the client workstation and the network resource;

computer readable program code means for causing a computer to name the second server in the fourth field;

computer readable program code means for causing a computer to recognize, on the basis of the fourth field of the first record, the backup server for the network resource as the second server;

computer readable program code means for monitoring across a common bus, at a second server, communications between the first server and the network resource across the common bus by noting a continual change in state of the network resource, and observing a termination in the communications between the first server and the network resource across the common bus by noting a stop in the continual change in state of the network resource; and

computer readable program code means for causing a computer to route communications between the client workstation and the network resource via the second server, responsive to said recognizing and detecting acts.

25. The computer readable program code means in said article of manufacture of claim 24, further comprising:

computer readable program code means for causing a computer to monitor the server named in the third field;

computer readable program code means for causing a computer to discover a recovery of the server named in the third field; and

computer readable program code means for causing a computer to re-route communications between the client workstation and the network resource via the first server, responsive to said monitoring and discovering acts.

26. The computer readable program code means in said article of manufacture of claim 25, wherein said computer readable program code means for causing a computer to discover a recovery, further includes:

computer readable program code means for causing a computer to send packets intermittently from the second server to the first server; and

computer readable program code means for causing a computer to re-acquire acknowledgments from the first server at the second server, the acknowledgments responsive to said sending act and to the recovery of said first server.

27. The computer readable program code means in said article of manufacture of claim 24, wherein said computer readable program code means for causing a computer to name, further includes:

computer readable program code means for causing a computer to allow a network administrator to name the primary server affiliation and the backup server affiliation in the third and fourth fields of the first record of the network resource database.

28. The computer readable program code means in said article of manufacture of claim 24, wherein said computer readable program code means for causing a computer to detect a failure, further includes:

computer readable program code means for causing a computer to send packets intermittently from the second server to the first server;

computer readable program code means for causing a computer to receive acknowledgments from the first server at the second server, the acknowledgments responsive to said sending act; and

computer readable program code means for causing a computer to notice a termination in the receipt of acknowledgments from the first server.