REPLICATING DATA IN A DATA STORAGE SYSTEM

• US 20170091044A1
• Filed: 09/30/2015
• Published: 03/30/2017
• Est. Priority Date: 09/30/2015
• Status: Active Grant

• Current Assignee: Kyndryl Incorporated
• Original Assignee: International Business Machines Corporation
• Inventors: Beeken, Christopher BE, Canto, Christopher, Cockburn, Gordon J., Wilkinson, John P.
• Granted Patent: US 10,303,360 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 11/2094 Redundant storage or storage space G06F11/2056 takes precedence
• CPC Class Codes: G06F 16/00 Information retrieval; Database structures therefor; File system structures therefor
• 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 3/06 Digital input from, or digital output to, record carriers , e.g. RAID, emulated record carriers or networked record carriers
• 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 3/0659 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]

Abstract

A first data storage device receives a first write request from a host device to update a first subset of the data regions and sends the first write request to a second data storage device. Prior to receiving a notification from the second device that it has been updated in accordance with the first write request, the first device receives a second write request from the second device to update a second subset of the data regions and one of the two devices is selected. If the first device is selected, the first device updates only its data regions that are in the second subset but not in the first subset according to the second write request. In the case that the second device is selected, the first device updates its data regions that are in the second subset according to the second write request.

Claims

1. A computer-implemented method of replicating data in a data storage system, wherein the data storage system comprises at least:

a first data storage device comprising a set of data regions;

a second data storage device comprising a set of data regions corresponding to the set of data regions of the first data storage device; and

a host device in communication with the first data storage device;

wherein the method comprises the steps of;

the first data storage device receiving a first write request from the host device to update a first subset of the data regions;

the first data storage device updating its data regions that are in the first subset in accordance with the first write request;

the first data storage device sending the first write request to the second data storage device;

prior to the first data storage device receiving a notification from the second data storage device that the second data storage device has been updated in accordance with the first write request, the first data storage device receiving a second write request from the second data storage device to update a second subset of the data regions;

selecting one of the first data storage device and the second data storage device using a characteristic of the first data storage device and the second data storage device;

in the case that the first data storage device is selected, the first data storage device updating only its data regions that are in the second subset but not in the first subset in accordance with the second write request; and

in the case that the second data storage device is selected, the first data storage device updating its data regions that are in the second subset in accordance with the second write request.

2. A method as claimed in claim 1, further comprising the step of the first data storage device sending a notification to the second data storage device that it has been updated in accordance with the second write request, wherein the notification comprises an indication of its updated data regions that were in the first subset and in the second subset.

3. A method as claimed in claim 1, further comprising the step of the first data storage device receiving a notification from the second data storage device that the second data storage device has been updated in accordance with the first write request, and in response sending a notification to the host device that the first write request has been completed.

4. A method as claimed in claim 1, further comprising the first data storage device receiving a notification from the second data storage device that the second data storage device has been updated in accordance with the first write request, and in response sending a flush message to the second data storage device.

5. A method as claimed in claim 1, further comprising the step of the first data storage device receiving a flush message from the second data storage device, and in response sending a flush message to the second data storage device.

6. A method as claimed in claim 5, wherein the first data storage device does not update its data regions in response to any further received write requests until the flush message is received from the second data storage device.

7. A method as claimed in claim 1, wherein the characteristic of the first data storage device and the second data storage device is the MAC address of the first data storage device and the second data storage device.

8. A first data storage device for replicating data with a second data storage device, the first data storage device comprising a set of data regions, and arranged to:

receive a first write request from a host device to update a first subset of the data regions;

update its data regions that are in the first subset in accordance with the first write request;

send the first write request to the second data storage device;

in the case it receives a second write request from the second data storage device to update a second subset of the data regions prior to it receiving a notification from the second data storage device that the second data storage device has been updated in accordance with the first write request, select one of the first data storage device and the second data storage device using a characteristic of the first data storage device and the second data storage device;

in the case that the first data storage device is selected, update only its data regions that are in the second subset but not in the first subset in accordance with the second write request; and

in the case that the second data storage device is selected, update its data regions that are in the second subset in accordance with the second write request.

9. A first data storage device as claimed in claim 8, further arranged to send a notification to the second data storage device that it has been updated in accordance with the second write request, wherein the notification comprises an indication of its updated data regions that were in the first subset and in the second subset.

10. A first data storage device as claimed in claim 8, further arranged to receive a notification from the second data storage device that the second data storage device has been updated in accordance with the first write request, and in response send a notification to the device that the first write request has been completed.

11. A first data storage device as claimed in claim 8, further arranged to receive a notification from the second data storage device that the second data storage device has been updated in accordance with the first write request, and in response send a flush message to the second data storage device.

12. A first data storage device as claimed in claim 8, further arranged to receive a flush message from the second data storage device, and in response send a flush message to the second data storage device.

13. A first data storage device as claimed in claim 12, further arranged to not update its data regions in response to any further received write requests until the flush message is received from the second data storage device.

14. A first data storage device as claimed in claim 8, wherein the characteristic of the first data storage device and the second data storage device is the MAC address of the first data storage device and the second data storage device.

15. A computer program product for replicating data in a data storage system comprising at least:

a first data storage device comprising a set of data regions;

a second data storage device comprising a set of data regions corresponding to the set of data regions of the first data storage device; and

a host device in communication with the first data storage device;

the computer program product comprising a computer-readable storage medium having program instructions embodied therewith, the program instructions comprising;

program instructions to receive a first write request from the host device to update a first subset of the data regions;

program instructions to update its data regions that are in the first subset in accordance with the first write request;

program instructions to send the first write request to the second data storage device;

prior to the first data storage device receiving a notification from the second data storage device that the second data storage device has been updated in accordance with the first write request, program instructions to receive a second write request from the second data storage device to update a second subset of the data regions;

program instructions to select one of the first data storage device and the second data storage device using a characteristic of the first data storage device and the second data storage device;

in the case that the first data storage device is selected, program instructions to update only its data regions that are in the second subset but not in the first subset in accordance with the second write request; and

in the case that the second data storage device is selected, program instructions to update its data regions that are in the second subset in accordance with the second write request.

16. The computer program product of claim 15, further comprising program instructions to send a notification to the second data storage device that it has been updated in accordance with the second write request, wherein the notification comprises an indication of its updated data regions that were in the first subset and in the second subset.

17. The computer program product of claim 15, further comprising program instructions to receive a notification from the second data storage device that the second data storage device has been updated in accordance with the first write request, and in response sending a notification to the host device that the first write request has been completed.

18. The computer program product of claim 15, further comprising program instructions to receive a notification from the second data storage device that the second data storage device has been updated in accordance with the first write request, and in response sending a flush message to the second data storage device.

19. The computer program product of claim 15, further comprising program instructions to receive a flush message from the second data storage device, and in response sending a flush message to the second data storage device.

20. The computer program product of claim 19, wherein the first data storage device does not update its data regions in response to any further received write requests until the flush message is received from the second data storage device.