DATA RESYNCHRONIZATION

• US 20190317667A1
• Filed: 04/13/2018
• Published: 10/17/2019
• Est. Priority Date: 04/13/2018
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Inventors: Killamsetti, Praveen, Barszczak, Tomasz, Sanghavi, Monil
• Granted Patent: US 10,956,079 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 12/0646 Configuration or reconfiguration
• 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
• CPC Class Codes: G06F 2212/1032 Reliability improvement, data loss prevention, degraded operation etc
• CPC Class Codes: G06F 2212/657 Virtual address space management
• CPC Class Codes: G06F 3/0611 in relation to response time
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: G06F 3/0671 In-line storage system

Abstract

Examples herein relate to re-synchronizing data between an upstream volume and a downstream volume, including by communicating data to the downstream volume, from a start point to an end point of the upstream volume, maintaining a first cursor to indicate data, from the start point to the first cursor, that has been communicated to and committed to persistent storage of the downstream volume, and maintaining a second cursor to indicate data, from the first cursor to the second cursor, that has been communicated to the downstream volume and buffered without yet being confirmed as committed to persistent storage of the downstream volume.

Claims

1. A method of re-synchronizing data between an upstream volume and a downstream volume, comprising:

communicating data to the downstream volume, from a start point to an end point of the upstream volume;

maintaining a first cursor to indicate data, from the start point to the first cursor, that has been communicated to and committed to persistent storage of the downstream volume; and

maintaining a second cursor to indicate data, from the first cursor to the second cursor, that has been communicated to the downstream volume and buffered without yet being confirmed as committed to persistent storage of the downstream volume.

2. The method of claim 1, comprising:

advancing the second cursor by an amount representing the amount of data that has been communicated to the downstream volume.

3. The method of claim 1, comprising:

receiving an acknowledgement message indicating that an amount of the buffered data has been committed to persistent storage of the downstream volume; and

advancing the first cursor by the amount, to indicate that the respective amount of data has been committed to persistent storage of the downstream volume.

4. The method of claim 1, comprising:

processing a write request to write new data to the upstream volume, comprising;

if the write operation is to write new data to the volume between the start point of the volume and the second cursor, writing the new data to persistent storage of the upstream volume and communicating the new data to the downstream volume to be replicated thereon;

if the write operation is to write the new data to a region of the volume that is locked from accepting write requests, suspending the write operation;

or

if the write operation is to write the new data to a region of the volume after the second cursor and that is not locked from accepting write requests, writing the new data to the upstream volume and not communicating the new data to the downstream volume to be replicated in response to the write request.

5. The method of claim 4, comprising, determining that new data that is communicated to the downstream volume is to overwrite data that has been committed to persistent storage of the downstream volume, and committing the new data to persistent storage of the downstream volume.

6. The method of claim 4, comprising, determining that new data that is communicated to the downstream volume is to overwrite data that has been buffered without yet being confirmed as committed to persistent storage of the downstream volume, and committing the buffered data to persistent storage of the downstream volume before committing the new data to persistent storage of the downstream volume.

7. The method of claim 1, comprising re-starting the re-synchronizing from the location of the first cursor in the event of a failure of the re-synchronizing.

8. A non-transitory computer-readable storage medium comprising instructions that, when executed by one or more processors, cause the one or more processors to re-synchronize data between a first data storage volume and a second data storage volume, wherein the instructions are executable to:

communicate data to the second data storage volume, from a start point to an end point of the first data storage volume;

maintain a first cursor to indicate how much of the data has been communicated to and committed to persistent storage of the second data storage volume; and

maintain, based on said communication, a second cursor to indicate how much data has been communicated to and buffered without yet being confirmed as committed to persistent storage of the second data storage volume.

9. The non-transitory computer-readable storage medium of claim 8, storing instructions that, when executed by one or more processors, cause the one or more processors to advance the first cursor by an amount representing the amount of data that has been communicated to the downstream volume.

10. The non-transitory computer-readable storage medium of claim 8, storing instructions that, when executed by one or more processors, cause the one or more processors to advance the second cursor by an amount representing the amount of data that has been committed to persistent storage of the second data storage volume, in response to receipt of a respective message indicating said amount.

11. The non-transitory computer-readable storage medium of claim 8, storing instructions that, when executed by one or more processors, cause the one or more processors to process a write request to write new data to the first data storage volume, wherein the instructions are executable to:

if the write operation is to write new data to the first data storage volume between the start point and the second cursor, write the new data to the first data storage volume and communicating the new data to the downstream volume to be replicated thereon;

if the write operation is to write the new data to a region of the first data storage volume that is locked, suspend the write operation;

or

if the write operation is to write the new data to a region of the first data storage volume after the second cursor and that is not locked, write the new data to the first data storage volume and not communicating the new data to the downstream volume to be replicated thereon.

12. The non-transitory computer-readable storage medium of claim 8, storing instructions that, when executed by one or more processors, cause the one or more processors, in the event of a failure of the resynchronizing, to re-start the resynchronizing from the location of the first cursor.

13. A storage apparatus to re-synchronize data in a downstream volume thereof with data from a system storing an upstream volume, comprising:

a first data buffer to receive given data that is to re-synchronize certain data in persistent storage of the downstream volume with the upstream volume;

a second data buffer to receive, after receipt of the given data into the first data buffer, new data that is to overwrite the certain data in the persistent storage of the downstream volume; and

a processor to execute stored instructions to commit to persistent storage of a current version of the downstream volume the new data in the second data buffer, after the given data in the first data buffer has been committed to persistent storage of the current version of the downstream volume, and to communicate an acknowledgement message to the system storing the upstream volume, the message indicating how much data has been committed to persistent storage of the current version of the downstream volume.

14. The storage apparatus according to claim 14, wherein the processor is to execute stored instructions to communicate an acknowledgement message to the system storing the upstream volume, the message indicating how much data has been committed from the first data buffer to persistent storage of the current version of the downstream volume.