LOW OVERHEAD FAULT TOLERANCE THROUGH HYBRID CHECKPOINTING AND REPLAY

• US 20100107158A1
• Filed: 10/28/2008
• Published: 04/29/2010
• Est. Priority Date: 10/28/2008
• Status: Active Grant

• Current Assignee: Vmware LLC (Broadcom, Inc.)
• Original Assignee: VMware, Inc. (Broadcom, Inc.)
• Inventors: CHEN, Peter M., GINZTON, Matthew D., SCALES, Daniel J., XU, Min
• Granted Patent: US 8,499,297 B2
• Time in Patent Office: Days
• US Class Current: 718/1
• CPC Class Codes: G06F 11/14 Error detection or correction of the data by redundancy in operation G06F11/16 takes precedence
• CPC Class Codes: G06F 11/1438 Restarting or rejuvenating
• CPC Class Codes: G06F 11/1446 Point-in-time backing up or restoration of persistent data
• CPC Class Codes: G06F 11/1458 Management of the backup or restore process
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 11/1484 involving virtual machines
• 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 11/203 using migration
• CPC Class Codes: G06F 11/2038 with a single idle spare processing component
• CPC Class Codes: G06F 16/188 Virtual file systems

Abstract

A virtualized computer system provides fault tolerant operation of a primary virtual machine. In one embodiment, this system includes a backup computer system that stores a snapshot of the primary virtual machine and a log file containing non-deterministic events occuring in the instruction stream of the primary virtual machine. The primary virtual machine periodically updates the snapshot and the log file. Upon a failure of the primary virtual machine, the backup computer can instantiate a failover backup virtual machine by consuming the stored snapshot and log file.

Claims

1. A method for providing fault-tolerance protection for a primary virtual machine using a snapshot image of the primary virtual machine that represents a state of the primary virtual machine at a time t₀, the method comprising:

tracking virtual machine instructions executed by the primary virtual machine since time t₀;

tracking a set of changes made to the state of the primary virtual machine since time t₀; and

merging the set of changes into the snapshot image, thereby creating a new snapshot image for a backup virtual machine.

2. The method of claim 1 further comprising the additional step of storing in a log file information relating to the tracked virtual machine instructions executed by the primary virtual machine.

3. The method of claim 2 further comprising the additional step of discarding from the log file any information relating to virtual machine instructions executed by the primary virtual machine prior to time t₀.

4. The method of claim 2 wherein the information relating to the tracked virtual machine instructions executed by the primary virtual machine since time t₀ corresponds to non-deterministic events occurring in the primary virtual machine'"'"'s instruction stream.

5. The method of claim 4 wherein the information includes timing of the non-deterministic events measured by the placement of the non-deterministic events in the primary virtual machine'"'"'s instruction stream.

6. The method of claim 5 wherein the information further includes data corresponding to non-deterministic external inputs to emulated devices of the primary virtual machine.

7. The method of claim 1 further comprising the additional step of discarding the tracked set of changes after the merging step.

8. The method of claim 1 wherein the merging step occurs upon receiving the set of changes.

9. The method of claim 1 further comprising the additional step of storing the set of changes made to the state of the primary virtual machine since time t₀.

10. The method of claim 9 wherein the merging step occurs upon a failure of the primary virtual machine.

11. The method of claim 1 further comprising the additional step of loading memory pages of the new snapshot image at the time the memory pages are needed during execution of the backup virtual machine'"'"'s instruction stream.

12. A virtualized computer platform adapted to provide failure-free operation of a primary virtual machine, the virtualized computer platform comprising:

a primary computer system comprising a processor programmed to execute a virtual machine software layer configured to (a) instantiate the primary virtual machine, (b) identify non-deterministic events occurring in the primary virtual machine'"'"'s instruction stream, and (c) periodically determine checkpoint changes made to the primary virtual machine'"'"'s state; and

a backup computer system coupled to the primary computer system, the backup computer system comprising a data store and a processor coupled to the data store, the processor programmed to (a) receive notification of a failure of the primary virtual machine, (b) retrieve from the data store a snapshot image of the primary virtual machine, (c) retrieve from the data store a log file containing information relating to non-deterministic events in the primary virtual machine'"'"'s instruction stream, and (d) provide the snapshot image and the log file to an instantiated backup virtual machine for restoring a state of the primary virtual machine by using the snapshot image and replaying a set of virtual machine instructions using the log file.

13. The virtualized computer platform of claim 12 wherein the processor of the backup computer system is further programmed to (a) periodically receive checkpoint changes from the primary computer system, and (b) merge the checkpoint changes into the snapshot image of the primary virtual machine stored in the data store.

14. The virtualized computer platform of claim 13 wherein the configuration to merge the checkpoint changes into the snapshot image of the primary virtual machine stored in the data store executes upon the failure of the primary virtual machine.

15. A computer readable storage medium having stored therein a computer program for providing a fault-tolerant virtual machine operating environment, wherein the computer program is configured to be executed on a primary computer system to carry out the steps of:

instantiating a primary virtual machine;

establishing a connection to a backup computer system;

transmitting a snapshot image of the primary virtual machine to the backup computer system;

logging information relating to virtual machine instructions executed by the primary virtual machine;

periodically determining a set of changes made to the state of the primary virtual machine; and

transmitting the set of changes to the backup computer system.

16. The computer readable storage medium of claim 15 wherein the computer program is further configured to be executed on the backup computer system to carry out the steps of:

storing in a log file the information relating to virtual machine instructions executed by the primary virtual machine; and

discarding from the log file any information relating to virtual machine instructions executed by the primary virtual machine prior to step of transmitting the set of changes.

17. The computer readable storage medium of claim 15 wherein the computer program is further configured to be executed on the backup computer system to carry out the step of merging the set of changes into the snapshot image thereby creating a new snapshot image reflecting a current state of the primary virtual machine.

18. The computer readable storage medium of claim 15 wherein the information relating to virtual machine instructions executed by the primary virtual machine corresponds to non-deterministic events occurring in the primary virtual machine'"'"'s instruction stream.

19. The computer readable storage medium of claim 16 wherein the computer program is further configured to be executed on the backup computer system to carry out the steps of:

instantiating a backup virtual machine;

merging the set of changes made to the primary virtual machine'"'"'s state into the snapshot image;

loading the snapshot image into the backup virtual machine; and

executing virtual machine instructions in the backup virtual machine based upon the log file.

20. The computer readable storage medium of claim 19 wherein the step of loading the snapshot image includes loading memory pages at the time the memory pages are needed during execution of the backup virtual machine'"'"'s instruction stream.