Consistency Group Volume Fast Resync Without Full CG Recovery
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Solution Overview
Problem
Existing cross-site storage solutions face challenges in efficiently managing individual volumes of a consistency group (CG) that transition out-of-synchronization (OOS) due to disruptive events, leading to potential I/O disruptions and failure to maintain zero recovery point objective (RPO) guarantees.
Innovation Solution
Implementing a Fast Resync process to bring individual volumes back into synchronization while allowing other CG members to remain synchronized, with a fallback to a CG-level resynchronization if the Fast Resync is unsuccessful within a time threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a CG-level resynchronization process is used to restore synchronization, then all volumes in the consistency group are resynchronized, but I/O disruptions occur and productivity is reduced
Solution Approach 1:
The patent segments the resynchronization process from the consistency group level to the individual volume level. When a disruptive event affects only one volume, the system performs Fast Resync on that specific volume rather than resynchronizing the entire CG, allowing other volumes to continue I/O operations without disruption.
Solution Approach 2:
The system applies partial action by performing resynchronization only on the affected volume pair(s) rather than the entire consistency group. The Fast Resync process targets specifically the volume that transitioned to OOS state, leaving other synchronized volumes untouched and operational.
2Productivity
If individual volume resynchronization is attempted, then I/O disruptions are minimized, but synchronization status of multiple volumes must be tracked and managed
Solution Approach 1:
The system implements feedback mechanisms through replication status indicators that continuously monitor the synchronization state of each volume pair. When a volume transitions to OOS state, the system detects this change and triggers the appropriate resynchronization process, then updates the status indicators to reflect the current synchronization state.
Solution Approach 2:
The system employs self-service through automatic detection and resolution of synchronization issues. The Fast Resync process is automatically initiated when a volume pair becomes out of sync, and the system autonomously manages the resynchronization without requiring manual intervention, reducing the complexity of synchronization management.
3Speed
If Fast Resync is used for individual volumes, then resynchronization speed is improved, but a fallback mechanism is needed if Fast Resync fails
Solution Approach 1:
The system prepares for potential Fast Resync failure by having the full CG-level resynchronization process as a pre-established fallback mechanism. If Fast Resync does not successfully restore synchronization within the expected time frame, the system automatically transitions to the CG-level process, ensuring that the fallback is already in place and does not require additional complexity during the recovery process.
Data Source
AI summary
Systems and methods are provided for bringing a volume of a consistency group (CG) into an in-synchronization (InSync) state while other volumes of the CG remain in the InSync state. According to an example, in order to support recovery from disruptive events in a manner that ensures a zero recovery point objective (RPO) guarantee and insulates an application making use of the CG from adverse impacts, responsive to a triggering event, a Fast Resync process may first be attempted to promptly bring an affected volume back into an in-synchronization (InSync) state from an out of synchronization (OOS) state while allowing other members of the CG to remain in the InSync state. Should the Fast resync process be unsuccessful in bringing the volume back into the InSync state within a predetermined or configurable time threshold, then a second type of resynchronization process may be employed at the CG level.