Virtual ordered writes

• US 20040193820A1
• Filed: 03/25/2003
• Published: 09/30/2004
• Est. Priority Date: 03/25/2003
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Ofer, Adi, Meiri, David, Kopylovitz, Haim, Moreshet, Hana, Yoder, Benjamin W., Halstead, Mark J.
• Granted Patent: US 6,898,685 B2
• Time in Patent Office: Days
• US Class Current: 711/167
• CPC Class Codes: G06F 11/2064 while ensuring consistency
• CPC Class Codes: G06F 11/2074 Asynchronous techniques
• CPC Class Codes: G06F 12/0868 Data transfer between cache memory and other subsystems, e.g. storage devices or host systems
• CPC Class Codes: G06F 12/0871 Allocation or management of cache space
• CPC Class Codes: G06F 2003/0697 device management, e.g. handlers, drivers, I/O schedulers
• CPC Class Codes: G06F 2201/82 Solving problems relating to consistency ensuring consistency in mirrored systems G06F11/2064
• CPC Class Codes: G06F 2212/284 being distributed
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0614 Improving the reliability of storage systems
• CPC Class Codes: G06F 3/0635 by changing the path, e.g. traffic rerouting, path reconfiguration
• CPC Class Codes: G06F 3/0656 Data buffering arrangements
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99955 Archiving or backup

Abstract

Ordering data writes include a host computer providing a plurality of data writes to a primary storage device, the primary storage device assigning a first sequence number to data writes begun after a first time and before a second time, the primary storage device assigning a second sequence number, different from the first sequence number, to data writes begun after the second time, in response to completion of all writes assigned the first sequence number, the primary storage device transferring writes assigned the first sequence number to a secondary storage device, and, in response to the primary storage device transferring all writes assigned the first sequence number to the secondary storage device, the primary storage device sending a commit message to the secondary storage device. Ordering data writes may also include, in response to receiving a commit message from the primary storage device, the secondary storage device storing the data writes having the first sequence number.

Claims

1. A method of ordering data writes, comprising:

a host computer providing a plurality of data writes to a primary storage device;

the primary storage device assigning a first sequence number to data writes begun after a first time and before a second time;

the primary storage device assigning a second sequence number, different from the first sequence number, to data writes begun after the second time;

in response to completion of all writes assigned the first sequence number, the primary storage device transferring writes assigned the first sequence number to a secondary storage device; and

in response to the primary storage device transferring all writes assigned the first sequence number to the secondary storage device, the primary storage device sending a commit message to the secondary storage device.

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

in response to receiving a commit message from the primary storage device, the secondary storage device storing the data writes having the first sequence number.

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

in response to storing all of the data writes having the first sequence number, the secondary storage device sending an acknowledge to the primary storage device.

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

following sending a commit message to the secondary storage device, the primary storage device suspending transferring data to the secondary storage device.

5. A method, according to claim 4, further comprising:

following suspending transferring data, the primary storage device assigning a third sequence number, different from the first and second sequence numbers, to subsequent data writes.

6. A method, according to claim 5, further comprising:

in response to the secondary storage device sending an acknowledge to the primary storage device, the primary storage device resuming transferring data to the secondary storage device.

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

providing data writes to cache slots of the primary storage device.

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

in response to a data write being assigned the second sequence number corresponding to a cache slot already assigned the first sequence number, copying the data to a new cache slot.

9. A method, according to claim 8, further comprising:

the primary storage device using a first list of pointers to the cache slots for data writes assigned the first sequence number; and

the primary storage device using a second list of pointers to the cache slots for data writes assigned the second sequence number.

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

providing a cache stamp field in a header portion of each of the slots, the cache stamp field including a sequence number associated with the slot.

11. A method, according to claim 10, wherein the cache stamp field also includes a password field that is written when the slot is first used.

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

in response to a slot no longer being used, clearing the password field.

13. A method, according to claim 8, further comprising:

the primary storage device using a first cache only virtual device for the cache slots corresponding to data writes assigned the first sequence number; and

the primary storage device using a second cache only virtual device for the cache slots corresponding to data writes assigned the second sequence number.

14. A method of storing ordered writes to a remote storage device, comprising:

receiving a commit message for data associated with a first sequence number;

in response to data associated with a second sequence number different from said first sequence number not yet being stored, waiting for the data associated with the second sequence number to be stored; and

initiating storage of the data associated with the first sequence number.

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

acknowledging the commit message.

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

constructing a list of modified slots in connection with receiving data associated with the first sequence number.

17. A method, according to claim 16, wherein initiating storage of data associated with the first sequence number includes traversing the list of modified slots.

18. Computer software that orders data writes, comprising:

executable code that assigns a first sequence number to data writes begun after a first time and before a second time;

executable code that assigns a second sequence number, different from the first sequence number, to data writes begun after the second time;

executable code that transfers writes assigned the first sequence number to a storage device in response to completion of all writes assigned the first sequence number; and

executable code that sends a commit message to the storage device after transferring all writes assigned the first sequence number.

19. Computer software, according to claim 18, further comprising:

executable code that suspends transferring data to the storage device after sending a commit message thereto.

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

executable code that assigns a third sequence number, different from the first and second sequence numbers, to subsequent data writes following suspending transferring data.

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

executable code that resumes transferring data to the storage device in response to the storage device acknowledging handling the commit.

22. Computer software, according to claim 18, further comprising:

executable code that provides data writes to cache slots.

23. Computer software, according to claim 22, further comprising:

executable code that copies data to a new cache slot in response to a data write being assigned the second sequence number corresponding to a cache slot already assigned the first sequence number.

24. Computer software, according to claim 23, further comprising:

executable code that uses a first list of pointers to the cache slots for data writes assigned the first sequence number; and

executable code that uses a second list of pointers to the cache slots for data writes assigned the second sequence number.

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

executable code that provides a cache stamp field in a header portion of each of the slots, the cache stamp field including a sequence number associated with the slot.

26. Computer software, according to claim 25, wherein the cache stamp field also includes a password field that is written when the slot is first used.

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

executable code that clears the password field in response to a slot no longer being used.

28. Computer software, according to claim 23, further comprising:

executable code that uses a first cache only virtual device for the cache slots corresponding to data writes assigned the first sequence number; and

executable code that uses a second cache only virtual device for the cache slots corresponding to data writes assigned the second sequence number.

29. Computer software that stores ordered writes to a remote storage device, comprising:

executable code that receives a commit message for data associated with a first sequence number;

executable code that waits for the data associated with the second sequence number to be stored in response to data associated with a second sequence number different from the first sequence number not yet being stored; and

executable code that initiates storage of the data associated with the first sequence number.

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

executable code that acknowledges the commit message.

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

executable code that constructs a list of modified slots in connection with receiving data associated with the first sequence number.

32. Computer software, according to claim 31, wherein executable code that initiates storage of data associated with the first sequence number includes executable code that traverses the list of modified slots.