SYNCHRONIZATION OF REPLICATED SEQUENTIAL ACCESS STORAGE COMPONENTS

• US 20110040942A1
• Filed: 08/11/2009
• Published: 02/17/2011
• Est. Priority Date: 08/11/2009
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: AKIRAV, Shay H., BACHAR, Yariv, DROBCHENKO, Elena, MELAMED, Dan, PAZ, Gil E., LAZAR, Aharon, KRIKLER, Samuel, MAOZ, Itay
• Granted Patent: US 8,296,536 B2
• Time in Patent Office: Days
• US Class Current: 711/159
• CPC Class Codes: G06F 11/1456 Hardware arrangements for backup
• CPC Class Codes: G06F 16/27 Replication, distribution or synchronisation of data between databases or within a distributed database system; Distributed database system architectures therefor

Abstract

Various embodiments for synchronization of source and replicated instances of sequential access storage components in a computing environment by a processor device are provided. A replication synchronization table (RST) is configured for the source instance. The RST is adapted for recording compacted information for at least one of a truncate and an erase operation applied on the source instance. The RST of the source instance is updated at a source component with the compacted information. The updated RST is transmitted from the source instance to the replicated instance. Based on the RST of the source instance and the RST of the replicated instance, data representative of a most recent position on the source component from which data should be transmitted to a replicated component to achieve a full synchronization is determined.

Claims

1. A method for synchronization of source and replicated instances of sequential access storage components in a computing environment by a processor device, comprising:

configuring a replication synchronization table (RST) for the source instance, wherein the RST is adapted for recording compacted information for at least one of a truncate and an erase operation applied on the source instance;

updating the RST of the source instance at a source component with the compacted information; and

determining, based on the RST of the source instance and the RST of the replicated instance, data representative of a most recent position on the source component from which data should be transmitted to a replicated component to achieve a full synchronization.

2. The method of claim 1, further including, based on the data representative of the most recent position, synchronizing the replicated instance with the source instance while updating the RST of the replicated instance with the data representative of the most recent position to reflect a synchronization status.

3. The method of claim 2, further including:

subsequent to the updating the RST of the source instance at the source component with the compacted information, transmitting the updated RST from the source instance to the replicated instance, and

subsequent to the determining the data representative of the most recent position on the source component, transmitting the data representative of the most recent position from the replicated instance to the source instance.

4. The method of claim 2, wherein the configuring the RST the source instance includes maintaining a current end of data (EOD) position for each of the source and replicated instances.

5. The method of claim 4, wherein the configuring the RST for the source instance includes configuring an entry in the RST to include fields for each of an operation identification value, a position value, and a unique system identification value.

6. The method of claim 5, wherein the updating the RST of the source instance at the source component with the compacted information includes:

for the at least one of the truncate and the erase operation, generating a new entry of the RST of the source instance,

if a write operation applies to a position smaller than the current EOD position for the source instance, determining the write operation to be the truncate operation,

appending the new entry to the RST of the source instance, and

if a first position value, based on the new entry, is one of smaller and equal to a second position value based on a most recent existing entry, removing all existing entries having position values one of larger and equal to the first position value.

7. The method of claim 6, wherein the generating the new entry further includes performing at least one of:

setting the first position value to a position in the new entry, and

setting a new unique system identification value of a generator of the new entry as a system identification in the new entry.

8. The method of claim 5, wherein the determining, based on the RST of the source instance and the RST of the replicated instance, the data representative of the most recent position on the source component from which the data should be transmitted to the replicated component to achieve the full synchronization includes:

locating a singular entry in the RST of the source instance at the source component having a maximum operation identification value of all entries in the RST having identical entries in the RST of the replicated instance at the replicated component,

if each of the singular entry and a succeeding entry in the RST of the source instance exists, and a succeeding entry of an identical entry of the singular entry in the RST of the replicated instance exists, calculating the most recent position as a first minimum value between a position value of the succeeding entry in the RST of the source instance, the current EOD position of the replicated instance, and a position value of the succeeding entry of the identical entry of the singular entry in the RST of the replicated instance.

9. The method of claim 8, wherein the determining further includes, if the succeeding entry in the RST of the identical entry of the replicated instance does not exist, calculating the most recent position as a second minimum value between the position value of the succeeding entry in the RST of the source instance and the current EOD position of the replicated instance.

10. The method of claim 9, wherein the determining further includes, if the singular entry exists and the succeeding entry in the RST of the source instance does not exist, and the succeeding entry of the identical entry of the singular entry in the RST of the replicated instance exists, calculating the most recent position as a third minimum value between the current EOD position of the replicated instance and the position value of the succeeding entry of the identical entry of the singular entry in the RST of the replicated instance.

11. The method of claim 10, wherein the determining further includes, if the singular entry exists and each of the succeeding entry in the RST of the source instance and the succeeding entry of the identical entry of the singular entry in the RST of the replicated instance does not exist, calculating the most recent position as the current EOD position of the replicated instance.

12. The method of claim 11, wherein the determining further includes, if the singular entry does not exist, calculating the most recent position as zero.

13. The method of claim 4, wherein the synchronizing the replicated instance with the source instance while updating the RST of the replicated instance with the data representative of the most recent position to reflect the synchronization status includes performing at least one of:

writing the data representative of the most recent position to a persistent storage location, and

advancing the current EOD position for the replicated instance.

14. The method of claim 13, wherein the synchronizing the replicated instance with the source instance while updating the RST of the replicated instance with the data representative of the most recent position to reflect the synchronization status further includes verifying the data representative of the most recent position using a mathematical digest.

15. The method of claim 13, wherein the synchronizing the replicated instance with the source instance while updating the RST of the replicated instance with the data representative of the most recent position to reflect the synchronization status further includes performing at least one of:

if the current EOD position for the replicated instance surpasses a first position value of the source instance, appending a new entry to the RST of the replicated instance such that each of an operation identification value, a position value, and a unique system identification value for the new entry of the RST of the replicated instance matches the new entry of the RST of the source instance, and

if the first position value of the source instance is one of smaller and equal to the second position value, removing all entries from the RST of the replicated instance having position values one of larger and equal to the first position value.

16. A system for synchronization of source and replicated instances of sequential access storage components in a computing environment, comprising:

a processor operable in the computing environment, wherein the processor is adapted for;

configuring a replication synchronization table (RST) for the source instance, wherein the RST is adapted for recording compacted information for at least one of a truncate and an erase operation applied on the source instance,

updating the RST of the source instance at a source component with the compacted information,

transmitting the updated RST from the source instance to the replicated instance,

determining, based on the RST of the source instance and the RST of the replicated instance, data representative of a most recent position on the source component from which data should be transmitted to a replicated component to achieve a full synchronization,

transmitting the data representative of the most recent position from the replicated instance to the source instance, and

based on the data representative of the most recent position, synchronizing the replicated instance with the source instance while updating the RST of the replicated instance with the data representative of the most recent position to reflect a synchronization status.

17. The system of claim 16, wherein the processor is further adapted for, pursuant to the configuring the RST for the source instance, maintaining a current end of data (EOD) position for each of the source and replicated instances.

18. The system of claim 17, wherein the processor is further adapted for, pursuant to the configuring the RST for the source instance, configuring an entry in the RST to include fields for each of an operation identification value, a position value, and a unique system identification value.

19. The system of claim 18, wherein the processor is further adapted for, pursuant to the updating the RST of the source instance at the source component with the compacted information:

for the at least one of the truncate and the erase operation, generating a new entry of the RST of the source instance,

if a write operation applies to a position smaller than the current EOD position for the source instance, determining the write operation to be the truncate operation,

appending the new entry to the RST of the source instance, and

if a first position value, based on the new entry, is one of smaller and equal to a second position value based on a most recent existing entry, removing all existing entries having position values one of larger and equal to the first position value.

20. The system of claim 19, wherein the processor is further adapted for, pursuant to the generating the new entry, performing at least one of:

setting the first position value to a position in the new entry, and

setting a new unique system identification value of a generator of the new entry as a system identification in the new entry.

21. The system of claim 18, wherein the processor is further adapted for, pursuant to the determining, based on the RST of the source instance and the RST of the replicated instance, the data representative of the most recent position on the source component from which the data should be transmitted to the replicated component to achieve the full synchronization:

locating a singular entry in the RST of the source instance at the source component having a maximum operation identification value of all entries in the RST having identical entries in the RST of the replicated instance at the replicated component,

if each of the singular entry and a succeeding entry in the RST of the source instance exists, and a succeeding entry of an identical entry of the singular entry in the RST of the replicated instance exists, calculating the most recent position as a first minimum value between a position value of the succeeding entry in the RST of the source instance, the current EOD position of the replicated instance, and a position value of the succeeding entry of the identical entry of the singular entry in the RST of the replicated instance.

22. The system of claim 21, wherein the processor is further adapted for, pursuant to the determining, if the succeeding entry in the RST of the identical entry of the replicated instance does not exist, calculating the most recent position as a second minimum value between the position value of the succeeding entry in the RST of the source instance and the current EOD position of the replicated instance.

23. The system of claim 21, wherein the processor is further adapted for, pursuant to the determining, if the singular entry exists and the succeeding entry in the RST of the source instance does not exist, and the succeeding entry of the identical entry of the singular entry in the RST of the replicated instance exists, calculating the most recent position as a third minimum value between the current EOD position of the replicated instance and the position value of the succeeding entry of the identical entry of the singular entry in the RST of the replicated instance.

24. The system of claim 22, wherein the processor is further adapted for, pursuant to the determining, if the singular entry exists and each of the succeeding entry in the RST of the source instance and the succeeding entry of the identical entry of the singular entry in the RST of the replicated instance does not exist, calculating the most recent position as the current EOD position of the replicated instance.

25. The system of claim 24, wherein the processor is further adapted for, pursuant to the determining, if the singular entry does not exist, calculating the most recent position as zero.

26. The method of claim 20, wherein the processor is further adapted for, pursuant to the synchronizing the replicated instance with the source instance while updating the RST of the replicated instance with the data representative of the most recent position to reflect the synchronization status, performing at least one of:

writing the data representative of the most recent position to a persistent storage location, and

advancing the current EOD position for the replicated instance.

27. The system of claim 26, wherein the processor is further adapted for, pursuant to the synchronizing the replicated instance with the source instance while updating the RST of the replicated instance with the data representative of the most recent position to reflect the synchronization status, verifying the data representative of the most recent position using a mathematical digest.

28. The system of claim 26, wherein the processor is further adapted for, pursuant to the synchronizing the replicated instance with the source instance while updating the RST of the replicated instance with the data representative of the most recent position to reflect the synchronization status, performing at least one of:

if the current EOD position for the replicated instance surpasses the first position value of the source instance, appending the new entry to the RST of the replicated instance such that each of the operation identification value, the position value, and the unique system identification value for the new entry of the RST of the replicated instance matches the new entry of the RST of the source instance, and

if the first position value of the source instance is one of smaller and equal to the second position value, removing all entries from the RST of the replicated instance having position values one of larger and equal to the first position value.

29. A computer program product for synchronization of source and replicated instances of sequential access storage components in a computing environment by a processor device, the computer program product comprising a computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program code portions comprising:

a first executable portion for configuring a replication synchronization table (RST) for the source instance, wherein the RST is adapted for recording compacted information for at least one of a truncate and an erase operation applied on the source instance;

a second executable portion for updating the RST of the source instance at a source component with the compacted information;

a third executable portion for transmitting the updated RST from the source instance to the replicated instance;

a fourth executable portion for determining, based on the RST of the source instance and the RST of the replicated instance, data representative of a most recent position on the source component from which data should be transmitted to a replicated component to achieve a full synchronization;

a fifth executable portion for transmitting the data representative of the most recent position from the replicated instance to the source instance; and

a sixth executable portion for, based on the data representative of the most recent position, synchronizing the replicated instance with the source instance while updating the RST of the replicated instance with the data representative of the most recent position to reflect a synchronization status.

30. The computer program product of claim 29, further including a seventh executable portion for, pursuant to the configuring the RST for the source instance, maintaining a current end of data (EOD) position for each of the source and replicated instances.

31. The computer program product of claim 30, further including an eighth executable portion for, pursuant to the configuring the RST for the source instance, configuring an entry in the RST to include fields for each of an operation identification value, a position value, and a unique system identification value.

32. The computer program product of claim 31, further including a ninth executable portion for, pursuant to the updating the RST of the source instance at the source component with the compacted information:

for the at least one of the truncate and the erase operation, generating a new entry of the RST of the source instance,

if a write operation applies to a position smaller than the current EOD position for the source instance, determining the write operation to be the truncate operation,

appending the new entry to the RST of the source instance, and

if a first position value, based on the new entry, is one of smaller and equal to a second position value based on a most recent existing entry, removing all existing entries having position values one of larger and equal to the first position value.

33. The computer program product of claim 32, further including a tenth executable portion for, pursuant to the generating the new entry, performing at least one of:

setting the first position value to a position in the new entry, and

setting a new unique system identification value of a generator of the new entry as a system identification in the new entry.

34. The computer program product of claim 31, further including a ninth executable portion for, pursuant to the determining, based on the RST of the source instance and the RST of the replicated instance, the data representative of the most recent position on the source component from which the data should be transmitted to the replicated component to achieve the full synchronization:

locating a singular entry in the RST of the source instance at the source component having a maximum operation identification value of all entries in the RST having identical entries in the RST of the replicated instance at the replicated component,

if each of the singular entry and a succeeding entry in the RST of the source instance exists, and a succeeding entry of an identical entry of the singular entry in the RST of the replicated instance exists, calculating the most recent position as a first minimum value between a position value of the succeeding entry in the RST of the source instance, the current EOD position of the replicated instance, and a position value of the succeeding entry of the identical entry of the singular entry in the RST of the replicated instance.

35. The computer program product of claim 34, further including a tenth executable portion for, pursuant to the determining, if the succeeding entry in the RST of the identical entry of the replicated instance does not exist, calculating the most recent position as a second minimum value between the position value of the succeeding entry in the RST of the source instance and the current EOD position of the replicated instance.

36. The computer program product of claim 35, further including an eleventh executable portion for, pursuant to the determining, if the singular entry exists and the succeeding entry in the RST of the source instance does not exist, and the succeeding entry of the identical entry of the singular entry in the RST of the replicated instance exists, calculating the most recent position as a third minimum value between the current EOD position of the replicated instance and the position value of the succeeding entry of the identical entry of the singular entry in the RST of the replicated instance.

37. The computer program product of claim 36, further including a twelfth executable portion for, pursuant to the determining, if the singular entry exists and each of the succeeding entry in the RST of the source instance and the succeeding entry of the identical entry of the singular entry in the RST of the replicated instance does not exist, calculating the most recent position as the current EOD position of the replicated instance.

38. The computer program product of claim 37, further including a thirteenth executable portion for, pursuant to the determining, if the singular entry does not exist, calculating the most recent position as zero.

39. The computer program product of claim 32, further including a tenth executable portion for, pursuant to the synchronizing the replicated instance with the source instance while updating the RST of the replicated instance with the data representative of the most recent position to reflect the synchronization status, performing at least one of:

writing the data representative of the most recent position to a persistent storage location, and

advancing the current EOD position for the replicated instance.

40. The computer program product of claim 39, further including an eleventh executable portion for, pursuant to the synchronizing the replicated instance with the source instance while updating the RST of the replicated instance with the data representative of the most recent position to reflect the synchronization status, verifying the data representative of the most recent position using a mathematical digest.

41. The computer program product of claim 39, further including an eleventh executable portion for, pursuant to the synchronizing the replicated instance with the source instance while updating the RST of the replicated instance with the data representative of the most recent position to reflect the synchronization status, performing at least one of:

if the current EOD position for the replicated instance surpasses the first position value of the source instance, appending the new entry to the RST of the replicated instance such that each of the operation identification value, the position value, and the unique system identification value for the new entry of the RST of the replicated instance matches the new entry of the RST of the source instance, and

if the first position value of the source instance is one of smaller and equal to the second position value, removing all entries from the RST of the replicated instance having position values one of larger and equal to the first position value.