Granted Patent B2

US 9,165,012 · App. 12/633,693 · Granted Oct 20, 2015

Abstract

Claims (51)

1. A periodic checkpoint method for a file system, comprising:

generating a first checkpoint at a first time on a file system replication source to maintain accessibility of the file system on the file system replication source, wherein the first checkpoint is a point-in-time snapshot of the file system;

performing an initial data replication of the file system from the file system replication source to a file system replication destination by transmitting first data from the first checkpoint to the file system replication destination;

identifying a set of data objects of the file system from the replication source that have been modified during a time period between the first time and a subsequent second time based on modification metadata for the set of data objects, wherein the modification metadata is maintained after a subsequent modification to the set of data objects;

generating a periodic checkpoint at the second time on the file system replication source by using the set of data objects, wherein the set of data objects is generated based on a modification time of files of the file system occurring between the first time and the second time;

transferring the modified data from the file system replication source to the file system replication destination in accordance with a second checkpoint;

determining whether the modified data has been successfully transmitted from the file system replication source to the file system replication destination;

instructing the file system replication source to retransmit at least a portion of the modified data when it is determined that the modified data has not been successfully transmitted;

determining whether the second checkpoint is stored at the file system replication source in response to the instruction;

retransmitting at least the portion of the modified data to the file system replication destination in accordance with the second checkpoint when it is determined that the second checkpoint is stored at the file system replication source; and

generating a third checkpoint and transmitting second data to the file system replication source associated with the third checkpoint when it is determined that the second checkpoint is no longer stored at the file system replication source.

2. The method of claim 1 , wherein the periodic checkpoint is free of data objects outside of the set of data objects.

3. The method of claim 1 , wherein a probability of an update incurring COW (copy on write) overhead in response to the periodic checkpoint is smaller than a probability of an update incurring COW overhead in response to a checkpoint preserving a point in time image of the file system in substantially its entirety.

4. The method of claim 1 , wherein the set of data objects is generated by examining whether the modification time of files of the file system falls between the first time and the second time.

5. The method of claim 1 , wherein the periodic checkpoint is isolated from user interface modification.

6. The method of claim 1 , wherein the periodic checkpoint taken at the second time is directed at preserving the files that have been modified after the first checkpoint.

7. The method of claim 1 , wherein a modification time data structure is maintained to track a plurality of modification times of files of the file system.

8. The method of claim 7 , wherein the modification time data structure is maintained user inaccessible.

9. The method of claim 8 , wherein the modification time data structure is updated in accordance with a modification to one or more files of the file system.

10. A non-transitory computer readable storage medium having stored thereon, computer executable instructions that, if executed by a computer system cause the computer system to perform a periodic checkpoint method for a file system comprising:

generating a first checkpoint at a first time on a file system replication source to maintain accessibility of the file system on the file system replication source, wherein the first checkpoint is a point-in-time snapshot of the file system;

performing an initial data replication of the file system from the file system replication source to a file system replication destination by transmitting first data from the first checkpoint to the file system replication destination;

identifying a set of data objects of the file system from the replication source that have been modified during a time period between the first time and a subsequent second time based on modification metadata for the set of data objects, wherein the modification metadata is maintained after a subsequent modification to the set of data objects;

generating a periodic checkpoint at the second time on the file system replication source by using the set of data objects, wherein the set of data objects is generated based on a modification time of files of the file system occurring between the first time and the second time;

transferring the modified data from the file system replication source to the file system replication destination in accordance with a second checkpoint;

determining whether the modified data has been successfully transmitted from the file system replication source to the file system replication destination;

instructing the file system replication source to retransmit at least a portion of the modified data when it is determined that the modified data has not been successfully transmitted;

determining whether the second checkpoint is stored at the file system replication source in response to the instruction;

retransmitting at least the portion of the modified data to the file system replication destination in accordance with the second checkpoint when it is determined that the second checkpoint is stored at the file system replication source; and

generating a third checkpoint and transmitting second data to the file system replication source associated with the third checkpoint when it is determined that the second checkpoint is no longer stored at the file system replication source.

11. The computer readable media of claim 10 , wherein the periodic checkpoint is isolated from user interface modification.

12. The computer readable media of claim 10 , wherein the periodic checkpoint taken at the second time is directed at preserving the files that are modified after the first checkpoint.

13. The computer readable media of claim 10 , wherein the periodic checkpoint is free of data objects outside of the set of data objects, and wherein a probability of an update incurring COW (copy on write) overhead in response to the periodic checkpoint is smaller than a probability of an update incurring COW overhead in response to a checkpoint preserving a point in time image of the file system in substantially its entirety.

14. The computer readable media of claim 10 , wherein a modification time data structure is maintained to track a plurality of modification times of files of the file system, and wherein the modification time data structure is user inaccessible.

15. A periodic file replication system, comprising:

a computer system having a processor coupled to a computer readable storage media and executing computer readable code which causes the computer system to implement a checkpoint manager module, wherein the checkpoint manager module:

generates a first checkpoint at a first time on a file system replication source to maintain accessibility of the file system on the file system replication source, wherein the first checkpoint is a point-in-time snapshot of the file system;

performs an initial data replication of the file system from the file system replication source to a file system replication destination by transmitting first data from the first checkpoint to the file system replication destination;

identifies a set of data objects of the file system from the replication source that have been modified during a time period between the first time and a subsequent second time based on modification metadata for the set of data objects, wherein the modification metadata is maintained after a subsequent modification to the set of data objects;

generates a periodic checkpoint at the second time on the file system replication source by using the set of data objects;

transfers the modified data from the file system replication source to the file system replication destination in accordance with a second checkpoint;

determines whether the modified data has been successfully transmitted from the file system replication source to the file system replication destination;

instructs the file system replication source to retransmit at least a portion of the modified data when it is determined that the modified data has not been successfully transmitted;

determine whether the second checkpoint is stored at the file system replication source in response to the instruction;

retransmit at least the portion of the modified data to the file system replication destination in accordance with the second checkpoint when it is determined that the second checkpoint is stored at the file system replication source; and

generate a third checkpoint and transmitting second data to the file system replication source associated with the third checkpoint when it is determined that the second checkpoint is no longer stored at the file system replication source.

16. The system of claim 15 , wherein the periodic checkpoint is free of data objects outside of the set of data objects.

17. The system of claim 15 , wherein the set of data objects is generated by examining whether a modification time of files of the file system falls between the first time and the second time.

18. The system of claim 15 , wherein the periodic checkpoint taken at the second time is directed at preserving the files that have been modified after the first checkpoint.

19. The system of claim 15 , wherein a modification time data structure is maintained to track a plurality of modification times of files of the file system, and wherein the modification time data structure is maintained user inaccessible.

20. The system of claim 19 , wherein the modification time data structure is updated in accordance with a modification to one or more files of the file system.

Assignments (11)