Preserving replication to a storage object on a storage node

• US 10,747,465 B2
• Filed: 10/30/2018
• Issued: 08/18/2020
• Est. Priority Date: 10/30/2018
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Inventors: Shang, Qiu, Subramanian, Vasu, Qu, Qi, Xiong, Tianfang, Qian, Yue
• Primary Examiner(s): Chery, Mardochee
• Application Number:
  US16/175,162
• Publication Number:
  US 20200133500A1
• Time in Patent Office: 658 Days
• Field of Search: 711154
• CPC Class Codes: G06F 11/2064 while ensuring consistency
• CPC Class Codes: G06F 11/2074 Asynchronous techniques
• CPC Class Codes: G06F 11/2076 Synchronous techniques
• CPC Class Codes: G06F 11/2082 Data synchronisation
• CPC Class Codes: G06F 16/178 Techniques for file synchronisation in file systems
• CPC Class Codes: G06F 16/184 implemented as replicated file system
• CPC Class Codes: G06F 3/0617 in relation to availability
• 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]

Abstract

A technique preserves replication to a storage node. The technique involves, from a first storage node, sending a replication query to a second storage node. The technique further involves, in response to the replication query sent to the second storage node, receiving replication session data from the second storage node. The replication session data describes replication which has terminated from a third storage node to the second storage node for a particular storage object. The technique further involves, based on the replication session data, establishing replication from the first storage node to the second storage node for the particular storage object to preserve use of the particular storage object.

Claims

1. A method of preserving replication to a storage node, the method comprising:

from a first storage node, sending a replication query to a second storage node;

in response to the replication query sent to the second storage node, receiving replication session data from the second storage node, the replication session data describing replication which has terminated between a third storage node and the second storage node for a particular storage object; and

based on the replication session data, establishing replication from the first storage node to the second storage node for the particular storage object to preserve use of the particular storage object;

wherein, prior to establishing replication from the first storage node to the second storage node, (i) a current version of the particular storage object resides on the first storage node and (ii) a non-current version of the particular storage object resides on the second storage node; and

wherein establishing replication from the first storage node to the second storage node for the particular storage object includes;

updating the non-current version of the particular storage object residing on the second storage node to match the current version of the particular storage object residing on the first storage node.

2. A method as in claim 1 wherein updating the non-current version of the particular storage object residing on the second storage node to match the current version of the particular storage object residing on the first storage node includes:

identifying a set of changes between the non-current version of the particular storage object residing on the second storage node and the current version of the particular storage object residing on the first storage node, and

sending only the set of changes from the first storage node to the second storage node to update the non-current version of the particular storage object residing on the second storage node in lieu of sending an entire copy of the current version of the particular storage object from the first storage node to the second storage node.

3. A method as in claim 2 wherein the current version of the particular storage object is formed from synchronous replication from the third storage node to the first storage node prior to a failover event;

wherein the non-current version of the particular storage object stored by the second storage node is formed by asynchronous replication from the third storage node to the second storage node prior to the failover event; and

wherein establishing replication from the first storage node to the second storage node further includes;

after the set of changes is sent from the first storage node to the second storage node to update the non-current version of the particular storage object, performing asynchronous replication from the first storage node to the second storage node for the particular storage object.

4. A method as in claim 1 wherein, prior to sending the replication query, asynchronous replication is performed from the third storage node to the second storage node for the particular storage object;

and

wherein sending the replication query to the second storage node includes;

providing the replication query to the second storage node after the asynchronous replication from the third storage node to the second storage node for the particular storage object has been terminated.

5. A method as in claim 4 wherein the asynchronous replication from the third storage node to the second storage node for the particular storage object is performed via an asynchronous replication session between the third storage node and the second storage node having (i) a replication session identifier that uniquely identifies the asynchronous replication session among other replication sessions and (ii) a recovery point objective (RPO) that identifies a target period in which data for the particular storage object might be lost due to an incident;

and

wherein receiving the replication session data from the second storage node includes;

acquiring, as at least a portion of the replication session data, the replication session identifier and the RPO from the second storage node.

6. A method as in claim 5 wherein establishing replication from the first storage node to the second storage node for the particular storage object further includes:

establishing an asynchronous replication session between the first storage node and the second storage node based on the replication session identifier and the RPO from the second storage node.

7. A method as in claim 1, further comprising:

while establishing replication from the first storage node to the second storage node for the particular storage object, concurrently establishing replication from the first storage node to the third storage node for the particular storage object.

8. A method as in claim 7 wherein establishing replication from the first storage node to the second storage node for the particular storage object further includes:

establishing an asynchronous replication session between the first storage node and the second storage node for the particular storage object, and

activating the asynchronous replication session to perform asynchronous replication from the first storage node to the second storage node for the particular storage object; and

wherein concurrently establishing replication from the first storage node to the third storage node for the particular storage object includes;

establishing a synchronous replication session between the first storage node and the third storage node for the particular storage object, and

activating the synchronous replication session to perform synchronous replication from the first storage node to the third storage node for the particular storage object.

9. A method as in claim 8 wherein activating the asynchronous replication session includes transitioning the asynchronous replication session to an active state;

and

wherein the method further comprises;

after the asynchronous replication session has been in the active state for a period of time, transitioning the asynchronous replication session from the active state to a hibernated state to deactivate replication from the first storage node to the second storage node for the particular storage object and enable the third storage node to perform replication to the second storage node for the particular storage object.

10. A method as in claim 1, further comprising:

prior to sending the replication query to the second storage node, performing replication to the second storage node for the particular storage object, and

terminating replication to the second storage node for the particular storage object.

11. A method as in claim 10 wherein performing replication to the second storage node for the particular storage object includes:

establishing an asynchronous replication session between the first storage node and the second storage node for the particular storage object, and

activating the asynchronous replication session to perform asynchronous, replication from the first storage node to the second storage node for the particular storage object; and

wherein terminating replication to the second storage node for the particular storage object includes;

deactivating the asynchronous replication session in response to a failover event.

12. A method as in claim 11 wherein activating the asynchronous replication session includes transitioning the asynchronous replication session to an active state;

wherein deactivating the asynchronous replication session includes transitioning the asynchronous replication session from the active state to a hibernated state; and

wherein establishing replication from the first storage node to the second storage node for the particular storage object includes transitioning the asynchronous replication session from the hibernated state back to the active state to reactivate the asynchronous replication session.

13. A method as in claim 1 wherein sending the replication query to the second storage node includes:

directing the second storage node to provide a list of replication sessions established between the third storage node and the second storage node.

14. A method as in claim 13 wherein receiving the replication session data from the second storage node includes:

obtaining the list of replication sessions established between the third storage node and the second storage node, the list of replication sessions identifying multiple inactive replication sessions established between the third storage node and the second storage node.

15. A method as in claim 14, further comprising:

while establishing replication from the first storage node to the second storage node for the particular storage object, establishing replication from the first storage node to the second storage node for other storage objects based on the multiple inactive replication sessions identified by the list.

16. A method as in claim 1 wherein, prior to establishing replication from the first storage node to the second storage node for the particular storage object, an earlier asynchronous replication session from the third storage node to the second storage node for the particular storage object is hibernated;

and

wherein establishing replication from the first storage node to the second storage node for the particular storage object includes;

reusing internal replication components at the second storage node to perform asynchronous replication from the first storage node to the second storage node.

17. A method as in claim 1 wherein, prior to sending the replication query, asynchronous replication is performed to the third storage node from the second storage node for the particular storage object;

and

wherein sending the replication query to the second storage node includes;

providing the replication query to the second storage node after the asynchronous replication to the third storage node from the second storage node for the particular storage object has been terminated.

18. Data storage equipment operating as a first storage node, comprising:

a communications interface;

memory; and

control circuitry coupled with the communications interface and the memory, the memory storing instructions which, when carried out by the control circuitry, causing the control circuitry to;

send a replication query to a second storage node through the communications interface,

in response to the replication query sent to the second storage node, receive replication session data from the second storage node through the communications interface, the replication session data describing replication which has terminated between a third storage node and the second storage node for a particular storage object, and

based on the replication session data, establish replication to the second storage node for the particular storage object to preserve use of the particular storage object;

wherein, prior to establishing replication from the first storage node to the second storage node, (i) a current version of the particular storage object resides on the first storage node and (ii) a non-current version of the particular storage object resides on the second storage node; and

wherein the control circuitry, when establishing replication from the first storage node to the second storage node for the particular storage object, is constructed and arranged to;

update the non-current version of the particular storage object residing on the second storage node to match the current version of the particular storage object residing on the first storage node.

19. A computer program product having a non-transitory computer readable medium which stores a set of instructions to preserve replication to a storage node;

the set of instructions, when carried out by a first storage node, causing the first storage node to perform a method of;

from the first storage node, sending a replication query to a second storage node;

in response to the replication query sent to the second storage node, receiving replication session data from the second storage node, the replication session data describing replication which has terminated between a third storage node and the second storage node for a particular storage object; and

based on the replication session data, establishing replication from the first storage node to the second storage node for the particular storage object to preserve use of the particular storage object;

wherein, prior to establishing replication from the first storage node to the second storage node, (i) a current version of the particular storage object resides on the first storage node and (ii) a non-current version of the particular storage object resides on the second storage node; and

wherein establishing replication from the first storage node to the second storage node for the particular storage object includes;

updating the non-current version of the particular storage object residing on the second storage node to match the current version of the particular storage object residing on the first storage node.

20. A method of preserving replication to a storage node, the method comprising:

from a first storage node, sending a replication query to a second storage node;

in response to the replication query sent to the second storage node, receiving replication session data from the second storage node, the replication session data describing replication which has terminated between a third storage node and the second storage node for a particular storage object; and

based on the replication session data, establishing replication from the first storage node to the second storage node for the particular storage object to preserve use of the particular storage object;

wherein the asynchronous replication from the third storage node to the second storage node for the particular storage object is performed via an asynchronous replication session between the third storage node and the second storage node having (i) a replication session identifier that uniquely identifies the asynchronous replication session among other replication sessions and (ii) a recovery point objective (RPO) that identifies a target period in which data for the particular storage object might be lost due to an incident; and

wherein receiving the replication session data from the second storage node includes;

acquiring, as at least a portion of the replication session data, the replication session identifier and the RPO from the second storage node.

21. A method of preserving replication to a storage node, the method comprising:

from a first storage node, sending a replication query to a second storage node;

in response to the replication query sent to the second storage node, receiving replication session data from the second storage node, the replication session data describing replication which has terminated between a third storage node and the second storage node for a particular storage object; and

based on the replication session data, establishing replication from the first storage node to the second storage node for the particular storage object to preserve use of the particular storage object;

wherein establishing replication from the first storage node to the second storage node for the particular storage object includes;

establishing an asynchronous replication session between the first storage node and the second storage node for the particular storage object, and

activating the asynchronous replication session to perform asynchronous replication from the first storage node to the second storage node for the particular storage object; and

wherein concurrently establishing replication from the first storage node to the third storage node for the particular storage object includes;

establishing a synchronous replication session between the first storage node and the third storage node for the particular storage object, and

activating the synchronous replication session to perform synchronous replication from the first storage node to the third storage node for the particular storage object.

22. A method of preserving replication to a storage node, the method comprising:

from a first storage node, sending a replication query to a second storage node;

in response to the replication query sent to the second storage node, receiving replication session data from the second storage node, the replication session data describing replication which has terminated between a third storage node and the second storage node for a particular storage object; and

based on the replication session data, establishing replication from the first storage node to the second storage node for the particular storage object to preserve use of the particular storage object;

wherein performing replication to the second storage node for the particular storage object includes;

establishing an asynchronous replication session between the first storage node and the second storage node for the particular storage object, and

activating the asynchronous replication session to perform synchronous replication from the first storage node to the second storage node for the particular storage object; and

wherein terminating replication to the second storage node for the particular storage object includes;

deactivating the asynchronous replication session in response to a failover event.