Method, system and program for maintaining data consistency among updates across groups of storage areas using update times

• US 6,463,501 B1
• Filed: 10/21/1999
• Issued: 10/08/2002
• Est. Priority Date: 10/21/1999
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Shackelford, David Michael, McBride, Gregory Edward, Kern, Ronald Maynard
• Primary Examiner(s): Gossage, Glenn
• Application Number:
  US09/422,595
• Time in Patent Office: 1,083 Days
• Field of Search: 711/112, 711/114, 711/161, 711/162, 711/165, 711/141, 711/100, 711/173, 714/5, 714/6, 714/7, 714/20, 707/201, 707/204, 707/202
• US Class Current: 711/100
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 11/2058 using more than 2 mirrored copies
• CPC Class Codes: G06F 11/2082 Data synchronisation
• CPC Class Codes: G06F 2201/82 Solving problems relating to consistency ensuring consistency in mirrored systems G06F11/2064
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A system, method, and program for maintaining data consistency among updates to data storage areas are provided. Each update has an update time the update was made. There are multiple groups of data storage areas. For each group, updates to the data storage area in the group are stored in a journal for storing updates to the group, wherein there are multiple journals. An indication is made in a memory area for each group of a group update time comprising a most recent update time of the updates in the group. The update time for each update in the group is not greater than the group update time. A determination is made of a minimum group update time across all the groups. At least one update is applied to storage if the update time for the update does not exceed the minimum group update time. The data storage areas may be partitioned among a plurality of computer systems, and may be maintained in at least one primary and secondary storage. The data storage areas may also comprise volumes, with each group including at least one volume. The groups of updates may also be maintained in a journal.

Claims

1. A method for maintaining data consistency among updates to data storage areas, wherein each update has an update time the update was made, comprising:

defining multiple groups of data storage areas;

for each group, storing updates to the data storage area in the group in a journal for storing updates to the group, wherein there are multiple journals;

for each group, indicating in a memory area a group update time of a most recent update time of the updates in the journal for the group, wherein the update time for each update in the group is not greater than the group update time;

determining a minimum group update time across all the groups; and

applying at least one update to storage from each journal if the update time for the update does not exceed the minimum group update time.

2. The method of claim 1, wherein the data storage areas are partitioned among a plurality of computer systems and wherein the groups are capable of defining updates to data storage areas across computer systems.

3. The method of claim 1, wherein the data storage areas are maintained in at least one primary and secondary storage device and wherein applying the update comprises writing the update to the data storage area in the secondary storage device.

4. The method of claim 1, further comprising:

receiving one update to one data storage area in one group; and

setting the most recent update time for the group including the received update to the update time for the received update.

5. The method of claim 1, further comprising:

storing received updates in a storage device, wherein applying the updates comprises writing the updates from the storage device to a storage system; and

during data recovery, applying updates in the storage device to the storage system.

6. The method of claim 1, further comprising:

determining for one group a point-in-time as of which no updates have been received for the storage areas within the group; and

setting the most recent update time for the one group to the determined point-in-time.

7. The method of claim 1, wherein the data storage areas comprise volumes, and wherein each group includes at least one volume.

8. The method of claim 1, wherein one data mover program is associated with each group, wherein, for each group, the data mover program stores the updates in the journal for the group and indicates in the memory area the group update time.

9. The method of claim 1, wherein the updates to the journal in each group are arranged in at least one consistency group such that the consistency group includes dependent updates and the updates from which the dependent updates depend as of a consistency time, and wherein consistency groups are formed in each journal independently of the consistency groups in the other journals.

10. The method of claim 9, further comprising applying all the updates in groups to storage if the update time of the update is less than the minimum group update time, wherein after applying the updates to storage, the data in the storage is consistent as of the minimum group update time.

11. The method of claim 1, wherein updates in the journal for each group are defined into at least one consistency group having a consistency time, further comprising:

selecting one consistency group within the journal for each selected group;

determining whether the consistency time of the selected consistency group is less than the minimum group update time; and

applying all the updates in the selected consistency group to storage if the consistency time of the selected consistency group is less than the minimum group update time.

12. The method of claim 11, further comprising reconsidering whether the consistency time of the selected consistency group is less than a current minimum group update time after a predetermined period of time if the consistency time is greater than the minimum group update time.

13. The method of claim 1, wherein updates in the journal for each group are defined into at least one consistency group having a consistency time, wherein consistency groups are formed in each journal independently of the consistency groups in the other journals, further comprising applying updates in consistency groups to storage if the update time of the update is less than the minimum group update time, wherein after applying the updates to storage, the data in the storage is consistent as of the minimum group update time.

14. The method of claim 13, wherein the updates in the consistency group are applied to storage during a data recovery operation, whereby not all of the updates in one consistency group will be applied to the secondary storage if the update time of at least one update in the consistency group is greater than the minimum group update time.

15. A system for maintaining data consistency, comprising:

data storage areas;

updates to the data storage areas, wherein each update has an update time the update was made;

a plurality of journals, wherein there is one journal for each group;

means for storing updates for each group to the data storage area in the group in the journal for storing updates to the group, wherein there are multiple journals;

means for defining multiple groups of data storage areas;

means for indicating in a memory area a group update time of a most recent update time of the updates in the journal for one group, wherein the update time for each update in the group is not greater than the group update time;

means for determining a minimum group update time across all the groups; and

means for applying at least one update to storage from each journal if the update time for the update does not exceed the minimum group update time.

16. The system of claim 15, wherein the data storage areas are partitioned among a plurality of computer systems and wherein the groups are capable of defining data storage areas across computer systems.

17. The system of claim 15, wherein the data storage areas are maintained in at least one primary and secondary storage device and wherein the means for applying the update comprises writing the update to the data storage area in the secondary storage device.

18. The system of claim 15, further comprising:

means for receiving one update to one data storage area in one group; and

means for setting the most recent update time for the group including the received update to the update time for the received update.

19. The system of claim 15, further comprising:

means for storing received updates in a storage device, wherein the means for applying the updates comprises writing the updates from the storage device to a storage system; and

means for applying updates in the storage device co the storage system during data recovery.

20. The system of claim 15, further comprising:

means for determining for one group a point-in-time as of which no updates have been received for the storage areas within the group; and

means for setting the most recent update time for the one group to the determined point-in-time.

21. The system of claim 15, wherein the data storage areas comprise volumes, and wherein each group includes at least one volume.

22. The system of claim 15, further comprising:

a plurality of data mover programs, wherein one data mover is associated with each group, and wherein the data mover for each group stores the updates in the journal for the group and indicates in the memory area the group update time.

23. The system of claim 15, wherein the updates to the journal in each group are arranged in at least one consistency group such that the consistency group includes dependent updates and the updates from which the dependent updates depend as of a consistency time, and wherein consistency groups are formed in each journal independently of the consistency groups in the other journals.

24. The system of claim 23, wherein the means for applying at least one update further performs applying all the updates in groups to storage if the update time of the update is less than the minimum group update time, wherein after applying the updates to storage, the data in the storage is consistent as of the minimum group update time.

25. The system of claim 15, wherein updates in the journal for each group are defined into at least one consistency group having a consistency time, further comprising:

means for selecting one consistency group within the journal for each selected group;

means for determining whether the consistency time of the selected consistency group is less than the minimum group update time, wherein the means for applying at least one update further performs applying all the updates in the selected consistency group to storage if the consistency time of the selected consistency group is less than the minimum group update time.

26. The system of claim 25, further comprising means for reconsidering whether the consistency time of the selected consistency group is less than a current minimum group update time after a predetermined period of time if the consistency time is greater than the minimum group update time.

27. The system of claim 15, wherein updates in the journal for each group are defined into at least one consistency group having a consistency time, wherein consistency groups are formed in each journal independently of the consistency groups in the other journals, wherein the means for applying at least one update further performs applying updates in consistency groups to storage if the update time of the update is less than the minimum group update time, wherein after applying the updates to storage, the data in the storage is consistent as of the minimum group update time.

28. The system of claim 27, wherein the updates in the consistency group are applied to storage during a data recovery operation, whereby not all of the updates in one consistency group will be applied to the secondary storage if the update time of at least one update in the consistency group is greater than the minimum group update time.

29. An article of manufacture for use in maintaining data consistency among updates to data storage areas, wherein each update has an update time the update was made, the article of manufacture comprising computer readable storage media including at least one computer program embedded therein capable of causing a processor to perform:

defining multiple groups of data storage areas;

for each group, storing updates to the data storage area in the group in a journal for storing updates to the group, wherein there are multiple journals;

for each group, indicating in a memory area a group update time of a most recent update time of the updates in the journal for the group, wherein the update time for each update in the group is not greater than the group update time;

determining a minimum group update time across all the groups; and

applying at least one update to storage from each journal if the update time for the update does not exceed the minimum group update time.

30. The article of manufacture of claim 29, wherein the data storage areas are partitioned among a plurality of computer systems and wherein the groups are capable of defining updates to data storage areas across computer systems.

31. The article of manufacture of claim 29, wherein the data storage areas are maintained in at least one primary and secondary storage device and wherein applying the update comprises writing the update to the data storage area in the secondary storage device.

32. The article of manufacture of claim 29, further comprising:

receiving one update to one data storage area in one group; and

setting the most recent update time for the group including the received update to the update time for the received update.

33. The article of manufacture of claim 29, further comprising:

storing received updates in a storage device, wherein applying the updates comprises writing the updates from the storage device to a storage system; and

during data recovery, applying updates in the storage device to the storage system.

34. The article of manufacture of claim 29, further comprising:

determining for one group a point-in-time as of which no updates have been received for the storage areas within the group; and

setting the most recent update time for the one group to the determined point-in-time.

35. The article of manufacture of claim 29, wherein the data storage areas comprise volumes, and wherein each group includes at least one volume.

36. The article of manufacture of claim 29, wherein the at least one computer program comprises one data mover program associated with each group, wherein, for each group, the data mover program stores the updates in the journal for the group and indicates in the memory area the group update time.

37. The article of manufacture of claim 29, wherein the updates to the journal in each group are arranged in at least one consistency group such that the consistency group includes dependent updates and the updates from which the dependent updates depend as of a consistency time, and wherein consistency groups are formed in each journal independently of the consistency groups in the other journals.

38. The article of manufacture of claim 37, further comprising applying all the updates in groups to storage if the update time of the update is less than the minimum group update time, wherein after applying the updates to storage, the data in the storage is consistent as of the minimum group update time.

39. The article of manufacture of claim 29, wherein updates in the journal for each group are defined into at least one consistency group having a consistency time, further comprising:

selecting one consistency group within the journal for each selected group;

determining whether the consistency time of the selected consistency group is less than the minimum group update time; and

applying all the updates in the selected consistency group to storage if the consistency time of the selected consistency group is less than the minimum group update time.

40. The article of manufacture of claim 39, further comprising reconsidering whether the consistency time of the selected consistency group is less than a current minimum group update time after a predetermined period of time if the consistency time is greater than the minimum group update time.

41. The article of manufacture of claim 29, wherein updates in the journal for each group are defined into at least one consistency group having a consistency time, wherein consistency groups are formed in each journal independently of the consistency groups in the other journals, further comprising applying updates in consistency groups to storage if the update time of the update is less than the minimum group update time, wherein after applying the updates to storage, the data in the storage is consistent as of the minimum group update time.

42. The article of manufacture of claim 41, wherein the updates in the consistency group are applied to storage during a data recovery operation, whereby not all of the updates in one consistency group will be applied to the secondary storage if the update time of at least one update in the consistency group is greater than the minimum group update time.