Regenerating a chain of backups

1. A method comprising:

creating, by a processor, a full backup image of a source volume, the full backup image corresponding to a state of the source volume at a first time;

tracking, in a first bitmap, changes to the source volume since the first time;

taking a first snapshot of the source volume at a second time, after the first time;

embedding the first bitmap into the first snapshot;

creating a first incremental backup image of the source volume by backing up the changes from the first snapshot according to the first bitmap;

merging a backup chain comprising the first incremental backup image and the full backup image to create a first synthetic full backup image, the first synthetic full backup image thereby corresponding to a state of the source volume at the second time, the state of the source volume at the first time now being lost because the full backup image has been merged with the first incremental backup image;

after the merge, retrieving the first bitmap embedded into the first snapshot of the source volume taken at the second time;

examining the first bitmap to identify the changes made to the source volume since the first time; and

based on the changes according to the first bitmap, regenerating the backup chain to obtain the full backup image and thereby the state of the source volume at the first time and not the second time.

2. The method of claim 1 wherein the first regenerated incremental backup image comprises data backed up from the source volume that changed between the first and second times and excludes data from the source volume that did not change between the first and second times.

3. The method of claim 1 further comprising:

maintaining, with the first snapshot, the first bitmap embedded into the first snapshot.

4. The method of claim 1 wherein after creation of the first synthetic full backup image of the source volume, the first incremental backup image of the source volume is no longer available because it has been merged with the full backup image of the source volume.

5. The method of claim 1 wherein the backup chain comprises a plurality of incremental backup images of the source volume,

wherein the plurality of incremental backup images are associated with a respective plurality of snapshots of the source volume taken at different times, each snapshot having a bitmap embedded, and

wherein each bitmap of a respective snapshot identifies data from the source volume that was to be copied to secondary storage for creation of a respective incremental backup image, and the method further comprises:

merging each of the plurality of incremental backup images into the full backup image to create a second synthetic full backup image of the source volume;

receiving a request to regenerate the backup chain comprising the plurality of incremental backup images;

retrieving a respective bitmap from the respective snapshot;

copying from the respective snapshot the data backed up from the source volume and identified by the respective bitmap to a respective regenerated incremental backup image; and

repeating the retrieving a respective bitmap and the copying from the respective snapshot until each of the plurality of incremental backup images of the source volume have been regenerated, thereby regenerating the backup chain.

6. The method of claim 5 further comprising:

after the backup chain has been regenerated, cutting one or more regenerated incremental backup images from the regenerated backup chain; and

merging each of one or more regenerated incremental backup images remaining in the regenerated backup chain into the full backup image to create a third synthetic full backup image of the source volume.

7. The method of claim 1 wherein each of the full backup image, first incremental backup image, and first synthetic full backup image are created by a same backup application.

8. A system for backup chain regeneration comprising: a processor;

and memory configured to store one or more sequences of instructions which, when executed by the processor, cause the processor to carry out the steps of:

creating a full backup image of a source volume, the full backup image corresponding to a state of the source volume at a first time;

tracking, in a first bitmap, changes to the source volume since the first time;

taking a first snapshot of the source volume at a second time, after the first time;

embedding the first bitmap into the first snapshot;

creating a first incremental backup image of the source volume by backing up the changes from the first snapshot according to the first bitmap;

merging a backup chain comprising the first incremental backup image and the full backup image to create a first synthetic full backup image, the first synthetic full backup image thereby corresponding to a state of the source volume at the second time, the state of the source volume at the first time now being lost because the full backup image has been merged with the first incremental backup image;

after the merge, retrieving the first bitmap embedded into the first snapshot of the source volume taken at the second time;

examining the first bitmap to identify the changes made to the source volume since the first time; and

based on the changes according to the first bitmap, regenerating the backup chain to obtain the full backup image and thereby the state of the source volume at the first time and not the second time.

9. The system of claim 8 wherein the first regenerated incremental backup image comprises data backed up from the source volume that changed between the first and second times and excludes data from the source volume that did not change between the first and second times.

10. The system of claim 8 wherein the processor further carries out the steps of:

maintaining, with the first snapshot, the first bitmap embedded into the first snapshot.

11. The system of claim 8 wherein after creation of the first synthetic full backup image of the source volume, the first incremental backup image of the source volume is no longer available because it has been merged with the full backup image of the source volume.

12. The system of claim 8 wherein the backup chain comprises a plurality of incremental backup images of the source volume,

wherein the plurality of incremental backup images are associated with a respective plurality of snapshots of the source volume taken at different times, each snapshot having a bitmap embedded, and

wherein each bitmap of a respective snapshot identifies data from the source volume that was to be copied to secondary storage for creation of a respective incremental backup image, and the process further carries out the steps of:

merging each of the plurality of incremental backup images into the full backup image to create a second synthetic full backup image of the source volume;

receiving a request to regenerate the backup chain comprising the plurality of incremental backup images;

retrieving a respective bitmap from the respective snapshot;

copying from the respective snapshot the data backed up from the source volume and identified by the respective bitmap to a respective regenerated incremental backup image; and

repeating the retrieving a respective bitmap and the copying from the respective snapshot until each of the plurality of incremental backup images of the source volume have been regenerated, thereby regenerating the backup chain.

13. The system of claim 12 wherein the processor further carries out the steps of:

after the backup chain has been regenerated, cutting one or more regenerated incremental backup images from the regenerated backup chain; and

merging each of one or more regenerated incremental backup images remaining in the regenerated backup chain into the full backup image to create a third synthetic full backup image of the source volume.

14. A computer program product, comprising a non-transitory computer-readable medium having a computer-readable program code embodied therein, the computer-readable program code adapted to be executed by one or more processors to implement a method for backup chain regeneration comprising:

creating a full backup image of a source volume, the full backup image corresponding to a state of the source volume at a first time;

tracking, in a first bitmap, changes to the source volume since the first time;

taking a first snapshot of the source volume at a second time, after the first time;

embedding the first bitmap into the first snapshot;

creating a first incremental backup image of the source volume by backing up the changes from the first snapshot according to the first bitmap;

merging a backup chain comprising the first incremental backup image and the full backup image to create a first synthetic full backup image, the first synthetic full backup image thereby corresponding to a state of the source volume at the second time, the state of the source volume at the first time now being lost because the full backup image has been merged with the first incremental backup image;

after the merge, retrieving the first bitmap embedded into the first snapshot of the source volume taken at the second time;

examining the first bitmap to identify the changes made to the source volume since the first time; and

based on the changes according to the first bitmap, regenerating the backup chain to obtain the full backup image and thereby the state of the source volume at the first time and not the second time.

15. The computer program product of claim 14 wherein the first regenerated incremental backup image comprises data backed up from the source volume that changed between the first and second times and excludes data from the source volume that did not change between the first and second times.

16. The computer program product of claim 14 wherein the method further comprises:

maintaining, with the first snapshot, the first bitmap embedded into the first snapshot.

17. The computer program product of claim 14 wherein after creation of the first synthetic full backup image of the source volume, the first incremental backup image of the source volume is no longer available because it has been merged with the full backup image of the source volume.

18. The computer program product of claim 14 wherein the backup chain comprises a plurality of incremental backup images of the source volume,

wherein the plurality of incremental backup images are associated with a respective plurality of snapshots of the source volume taken at different times, each snapshot having a bitmap embedded, and

wherein each bitmap of a respective snapshot identifies data from the source volume that was to be copied to secondary storage for creation of a respective incremental backup image, and the method further comprises:

merging each of the plurality of incremental backup images into the full backup image to create a second synthetic full backup image of the source volume;

receiving a request to regenerate the backup chain comprising the plurality of incremental backup images;

retrieving a respective bitmap from the respective snapshot;

copying from the respective snapshot the data backed up from the source volume and identified by the respective bitmap to a respective regenerated incremental backup image; and

repeating the retrieving a respective bitmap and the copying from the respective snapshot until each of the plurality of incremental backup images of the source volume have been regenerated, thereby regenerating the backup chain.

19. The computer program product of claim 18 wherein the method further comprises:

after the backup chain has been regenerated, cutting one or more regenerated incremental backup images from the regenerated backup chain; and

merging each of one or more regenerated incremental backup images remaining in the regenerated backup chain into the full backup image to create a third synthetic full backup image of the source volume.