Coordinated snapshots among storage systems implementing a promotion/demotion model

1. A method comprising:

monitoring a set of two or more target storage systems, wherein the two or more target storage systems are replication targets for respective portions of a source dataset;

associating a first coordinated tracking dataset with two or more local tracking datasets maintained on the two or more target storage systems, wherein each local tracking dataset is a tracking copy for one portion of the source dataset; and

advancing, in dependence upon a first coordinated target checkpoint, the first coordinated tracking dataset, wherein the first coordinated target checkpoint is associated with a set of local replicated checkpoints replicated from a set of source storage systems and the set of local replicated checkpoints is associated with a coordinated source checkpoint for the dataset.

2. The method of claim 1 , wherein the coordinated source checkpoint is a snapshot coordinated across the set of source storage systems; and wherein the first coordinated target checkpoint is a coordinated replicated snapshot.

3. The method of claim 1 , wherein a storage implementation of a first target storage system among the two or more target storage systems is one of a block storage implementation, a file system implementation, a database implementation, and an object store implementation;

wherein a storage implementation of a second target storage system among the two or more target storage systems is one of a block storage implementation, a file system implementation, a database implementation, and an object store implementation; and

wherein the storage implementation of the first target storage system is different from the storage implementation of the second target storage system.

4. The method of claim 1 , wherein the two or more target storage systems are respectively paired with at least one of two or more source storage systems by respective replication links to form a plurality of replicating pairs; and

wherein each of the two or more source storage systems stores a distinct local portion of the source dataset.

5. The method of claim 1 further comprising:

identifying a second coordinated target checkpoint, wherein the second coordinated target checkpoint is incomplete; and

creating, in dependence upon the second coordinated target checkpoint, a second coordinated tracking dataset.

6. The method of claim 1 further comprising:

promoting, in response to a promotion event, the first coordinated tracking dataset.

7. The method of claim 6 , wherein the source dataset, stored across a set of source storage systems, remains promoted.

8. The method of claim 6 , wherein the source dataset, stored across a set of source storage systems, is demoted in response to a demotion event.

9. The method of claim 8 , wherein, in response to the demotion event, a coordinated source checkpoint is established; and wherein the established coordinated source checkpoint is replicated from the set of source storage systems to the set of target storage systems.

10. The method of claim 8 , wherein a target coordinator and a source coordinator coordinate the promotion of the first coordinated tracking dataset across the set of target storage systems and the demotion of the source dataset across the set of source storage systems.

11. The method of claim 1 further comprising:

coordinating a clone of the first coordinated tracking dataset.

12. An apparatus comprising a computer processor, a computer memory operatively coupled to the computer processor, the computer memory having disposed within it computer program instructions that, when executed by the computer processor, cause the apparatus to:

monitor a set of two or more target storage systems, wherein the two or more target storage systems are replication targets for respective portions of a source dataset;

associate a first coordinated tracking dataset with two or more local tracking datasets maintained on the two or more target storage systems, wherein each local tracking dataset is a tracking copy for one portion of the source dataset; and

advance, in dependence upon a first coordinated target checkpoint, the first coordinated tracking dataset, wherein the first coordinated target checkpoint is associated with a set of local replicated checkpoints replicated from a set of source storage systems and the set of local replicated checkpoints is associated with a coordinated source checkpoint for the dataset.

13. The apparatus of claim 12 further comprising computer program instructions that cause the apparatus to:

identify a second coordinated target checkpoint, wherein the second coordinated target checkpoint is incomplete; and

create, in dependence upon the second coordinated target checkpoint, a second coordinated tracking dataset.

14. The apparatus of claim 12 further comprising computer program instructions that cause the apparatus to:

promote, in response to a promotion event, the first coordinated tracking dataset.

15. The apparatus of claim 12 further comprising computer program instructions that cause the apparatus to:

coordinate a clone of the first coordinated tracking dataset.

16. A non-transitory computer program product disposed upon a computer readable medium, the computer program product comprising computer program instructions that, when executed by a processor, cause a computer to:

monitor a set of two or more target storage systems, wherein the two or more target storage systems are replication targets for respective portions of a source dataset;

associate a first coordinated tracking dataset with two or more local tracking datasets maintained on the two or more target storage systems, wherein each local tracking dataset is a tracking copy for one portion of the source dataset; and

advance, in dependence upon a first coordinated target checkpoint, the first coordinated tracking dataset, wherein the first coordinated target checkpoint is associated with a set of local replicated checkpoints replicated from a set of source storage systems and the set of local replicated checkpoints is associated with a coordinated source checkpoint for the dataset.

17. The computer program product of claim 16 further comprising computer program instructions that cause the computer to:

identify a second coordinated target checkpoint, wherein the second coordinated target checkpoint is incomplete; and

create, in dependence upon the second coordinated target checkpoint, a second coordinated tracking dataset.

18. The computer program product of claim 16 further comprising computer program instructions that cause the computer to:

promote, in response to a promotion event, the first coordinated tracking dataset.

19. The computer program product of claim 16 further comprising computer program instructions that cause the computer to:

coordinate a clone of the first coordinated tracking dataset.