Switching between virtual ordered writes mode and synchronous or semi-synchronous RDF transfer mode

• US 20050198454A1
• Filed: 03/08/2004
• Published: 09/08/2005
• Est. Priority Date: 03/08/2004
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Meiri, David, Yoder, Benjamin W., Longinov, Vadim
• Granted Patent: US 7,228,396 B2
• Time in Patent Office: Days
• US Class Current: 711/162
• CPC Class Codes: G06F 11/2064 while ensuring consistency
• CPC Class Codes: G06F 11/2071 using a plurality of controllers
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 2201/835 Timestamp
• CPC Class Codes: G06F 2212/285 Redundant cache memory

Abstract

Transitioning from a first data transfer mode to a second data transfer mode that is different from the first data transfer mode includes a primary storage device receiving a plurality of data writes while being in the first data transfer mode, the primary storage device associating data writes begun after a first time and before a second time with a first chunk of data, the primary storage device associating data writes begun after the second time with a second chunk of data different from the first chunk of data, and the primary storage device transitioning to the second data transfer mode after the second time by first transferring writes associated with the first chunk of data to a secondary storage device after completion of all writes associated with the first chunk of data and then, after all writes associated with the first chunk of data have been transferred to the secondary storage device, transferring writes associated with the second chunk of data to the secondary storage device using the first data transfer mode, where writes begun after initiating transitioning are provided to the secondary storage device using the second data transfer mode. Transitioning from a first data transfer mode to a second data transfer mode that is different from the first data transfer mode may also include, following the primary storage device transferring all writes associated with the first chunk of data to the secondary storage device, the primary storage device sending a message to the secondary storage device, and, in response to receiving the message from the primary storage device, the secondary storage device storing the data writes associated with the first chunk of data.

Claims

1. A method of transitioning from a first data transfer mode to a second data transfer mode that is different from the first data transfer mode, the method comprising:

a primary storage device receiving a plurality of data writes while being in the first data transfer mode;

the primary storage device associating data writes begun after a first time and before a second time with a first chunk of data;

the primary storage device associating data writes begun after the second time with a second chunk of data different from the first chunk of data; and

the primary storage device transitioning to the second data transfer mode after the second time by first transferring writes associated with the first chunk of data to a secondary storage device after completion of all writes associated with the first chunk of data and then, after all writes associated with the first chunk of data have been transferred to the secondary storage device, transferring writes associated with the second chunk of data to the secondary storage device using the first data transfer mode, wherein writes begun after initiating transitioning are provided to the secondary storage device using the second data transfer mode.

2. A method, according to claim 1, further comprising:

following the primary storage device transferring all writes associated with the first chunk of data to the secondary storage device, the primary storage device sending a message to the secondary storage device; and

in response to receiving the message from the primary storage device, the secondary storage device storing the data writes associated with the first chunk of data.

3. A method, according to claim 2, further comprising:

after storing all of the data writes associated with the first chunk of data, the secondary storage device sending an acknowledge to the primary storage device.

4. A method, according to claim 1, wherein, in the second data transfer mode, the primary storage device acknowledges a write thereto in response to the secondary storage device acknowledging receipt of data corresponding to the write.

5. A method, according to claim 1, wherein, in the second data transfer mode, the primary storage device acknowledges a write thereto in response to the secondary storage device acknowledging receipt of data previously written to a storage location thereof corresponding to the write.

6. A method, according to claim 5, wherein the primary storage device acknowledges the write prior to the secondary storage device acknowledging receipt of data corresponding to the write.

7. A method, according to claim 1, further comprising:

following transitioning to the second data transfer mode, the primary storage device transferring writes associated with the second chunk of data to the secondary storage device.

8. A method, according to claim 7, wherein a subset of the writes associated with the second chunk are transferred using the second data transfer mode.

9. A method, according to claim 1, further comprising:

prior to transitioning from the first data transfer mode to the second data transfer mode, inhibiting creation of additional chunks of data.

10. A method, according to claim 1, further comprising:

the primary storage device sending a message to the secondary storage device indicating the transitioning from the first data transfer mode to the second data transfer mode.

11. A method, according to claim 1, further comprising:

in response to a data write occurring prior to transferring all writes associated with the first chunk of data to the secondary storage device, associating the write with the second chunk of data.

12. A method, according to claim 1, further comprising:

in response to a data write occurring after transferring all writes associated with the first chunk of data to the secondary storage device and before transferring all writes associated with the second chunk of data to the secondary storage device, merging the write with data in the second chunk of data if the write corresponds to data already in the second chunk of data.

13. A method, according to claim 1, further comprising:

in response to a data write occurring after transferring all writes associated with the first chunk of data to the secondary storage device and before transferring all writes associated with the second chunk of data to the secondary storage device, transferring the data using the second data transfer mode if the write does not correspond to data already in the second chunk of data.

14. A method, according to claim 1, further comprising:

providing a transition variable that is periodically incremented to indicate a state of the transition, wherein the transition variable is used to select the first mode or the second mode for writes that occur after initiation of the transition.

15. A method of storing data provided to a remote storage device, comprising:

receiving a first plurality of writes associated with a first chunk of data;

receiving a second plurality of writes associated with a second chunk of data, wherein the second plurality of writes are all begun after the first plurality of writes;

receiving a message indicating a transition from a first data transfer mode to a second data transfer mode;

initiating storage of the first and second plurality of writes; and

receiving writes provided according to one of;

the first data transfer mode and the second data transfer mode, wherein a received write corresponding to data in one of the chunks is merged with the data in one of the chunks.

16. A method, according to claim 15, wherein a received write that does not correspond to data in one of the chunks is stored according to the second data transfer mode.

17. A method, according to claim 15, wherein initiating storage of the first and second plurality of writes includes completing storage of the first plurality of writes prior to beginning storage of the second plurality of writes.

18. A method, according to claim 15, further comprising:

returning a first type of acknowledge message in response to receiving a write provided according to the first data transfer mode; and

returning a second type of acknowledge message in response to receiving a write provided according to the second data transfer mode.

19. Computer software that handles transitioning from a first data transfer mode to a second data transfer mode that is different from the first data transfer mode, the software comprising:

executable code on a primary storage device that receives a plurality of data writes while being in the first data transfer mode;

executable code that associates data writes begun after a first time and before a second time with a first chunk of data;

executable code that associates data writes begun after the second time with a second chunk of data different from the first chunk of data; and

executable code that responds to a transition to the second data transfer mode after the second time by first initiating transfer of writes associated with the first chunk of data to a secondary storage device after completion of all writes associated with the first chunk of data and then, after all writes associated with the first chunk of data have been transferred to the secondary storage device, transferring subsequent data to the secondary storage device using the first data transfer mode, wherein writes begun after initiating transitioning are provided to the secondary storage device using the second data transfer mode.

20. Computer software, according to claim 19, further comprising:

executable code that sends a message to the secondary storage device following the primary storage device transferring all writes associated with the first chunk of data to the secondary storage device.

21. Computer software, according to claim 19, wherein, in the second data transfer mode, the primary storage device acknowledges a write thereto in response to the secondary storage device acknowledging receipt of data corresponding to the write.

22. Computer software, according to claim 19, wherein, in the second data transfer mode, the primary storage device acknowledges a write thereto in response to the secondary storage device acknowledging receipt of data previously written to a storage location thereof corresponding to the write.

23. Computer software, according to claim 22, wherein the primary storage device acknowledges the write prior to the secondary storage device acknowledging receipt of data corresponding to the write.

24. Computer software, according to claim 19, further comprising:

executable code that transfers writes associated with the second chunk of data to the secondary storage device following transitioning to the second data transfer mode.

25. Computer software, according to claim 24, wherein a subset of the writes associated with the second chunk are transferred using the second data transfer mode.

26. Computer software, according to claim 19, further comprising:

executable code that inhibits creation of additional chunks of data prior to transitioning from the first data transfer mode to the second data transfer mode.

27. Computer software, according to claim 19, further comprising:

executable code that sends a message to the secondary storage device indicating the transitioning from the first data transfer mode to the second data transfer mode.

28. Computer software, according to claim 19, further comprising:

executable code that associates a data write with the second chunk of data when the data write occurs prior to transferring all writes associated with the first chunk of data to the secondary storage device.

29. Computer software, according to claim 19, further comprising:

executable code that merges a write with data in the second chunk of data if the write corresponds to data already in the second chunk of data when the data write occurs after transferring all writes associated with the first chunk of data to the secondary storage device and before transferring all writes associated with the second chunk of data to the secondary storage device.

30. Computer software, according to claim 19, further comprising:

executable code that transfers a write using the second data transfer mode if the write does not correspond to data already in the second chunk of data when the data write occurs after transferring all writes associated with the first chunk of data to the secondary storage device and before transferring all writes associated with the second chunk of data to the secondary storage device.

31. Computer software, according to claim 19, further comprising:

executable code that provides a transition variable that is periodically incremented to indicate a state of the transition, wherein the transition variable is used to select the first mode or the second mode for writes that occur after initiation of the transition.

32. Computer software that stores data provided to a remote storage device, comprising:

executable code that receives a first plurality of writes associated with a first chunk of data;

executable code that receives a second plurality of writes associated with a second chunk of data, wherein the second plurality of writes are all begun after the first plurality of writes;

executable code that receives a message indicating a transition from a first data transfer mode to a second data transfer mode;

executable code that initiates storage of the first and second plurality of writes; and

executable code that receives writes provided according to one of;

the first data transfer mode and the second data transfer mode, wherein a received write corresponding to data in one of the chunks is merged with the data in one of the chunks.

33. Computer software, according to claim 32, wherein a received write that does not correspond to data in one of the chunks is stored according to the second data transfer mode.

34. Computer software, according to claim 32, wherein executable code that initiates storage of the first and second plurality of writes includes executable code that completes storage of the first plurality of writes prior to beginning storage of the second plurality of writes.

35. Computer software, according to claim 32, further comprising:

executable code that returns a first type of acknowledge message in response to receiving a write provided according to the first data transfer mode; and

executable code that returns a second type of acknowledge message in response to receiving a write provided according to the second data transfer mode.

36. A data storage device, comprising:

at least one disk drive that contains data;

at least one host adaptor, coupled to the at least one disk drive, that receives data to be stored on the at least one disk drive; and

at least one remote adaptor, coupled to the at least one disk drive and the at least one host adaptor, that transmits data to a remote storage device, wherein, in response to receipt of data by the at least one host adaptor, data writes begun after a first time and before a second time are associated with a first chunk of data, data writes begun after the second time are associated with a second chunk of data different from the first chunk of data and, a transition from a first data transfer mode to a second data transfer mode is provided by first initiating transfer of writes associated with the first chunk of data to a secondary storage device after completion of all writes associated with the first chunk of data and then, after all writes associated with the first chunk of data have been transferred to the secondary storage device, transferring subsequent data to the secondary storage device using the first data transfer mode, wherein writes begun after initiating transitioning are provided to the secondary storage device using the second data transfer mode.