On-Demand Remote Snapshot Creation in Synchronous Replication
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Solution Overview
Problem
In high-performance storage systems with synchronous replication, creating a point-in-time snapshot is challenging due to system states like interim_async and async_to_sync, where data consistency may not be maintained, and existing solutions interfere with automatic recovery processes.
Innovation Solution
A method and system for on-demand remote snapshot creation in synchronous replication sessions, which identifies the current state of the replication session and performs necessary actions before transitioning to another state, allowing for snapshot creation while preserving high availability and automatic recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If synchronous replication is implemented to maintain data consistency, then data reliability is improved, but system complexity increases due to multiple replication states (interim_async, async_to_sync, steady_sync)
Solution Approach 1:
The patent checks the replication session state before creating a snapshot and performs preliminary actions (waiting for state transition or creating snapshot in interim_async state) to ensure data consistency. This preliminary state verification prevents inconsistent snapshots while maintaining system reliability across different replication states.
2Ease of operation
If snapshot creation is allowed during all replication states, then ease of operation is improved, but data consistency deteriorates in interim_async and async_to_sync states
Solution Approach 1:
The patent dynamically adjusts snapshot creation behavior based on the current replication session state. In steady_sync state, snapshots are created immediately; in interim_async state, snapshots are created with asynchronous replication; in async_to_sync state, the system waits for state transition. This dynamic approach balances operational ease with data consistency requirements.
Solution Approach 2:
The system continuously monitors the replication session state and uses this feedback to determine the appropriate snapshot creation action. The state machine provides feedback about the current replication phase, which controls whether snapshot creation should proceed immediately, wait, or use alternative methods, ensuring consistency while maintaining usability.
3Productivity
If automatic recovery processes are allowed to proceed without interruption, then productivity is improved, but snapshot creation capability deteriorates during recovery transitions
Solution Approach 1:
The patent performs preliminary checks of the replication session state before allowing snapshot creation during automatic recovery. If the system is in a safe state (steady_sync or interim_async), snapshots can be created without interrupting recovery. If the system is in async_to_sync state during recovery, the patent waits for the transition to complete before creating snapshots, ensuring recovery productivity is maintained while enabling snapshot capability when safe.
Data Source
AI summary
An aspect of performing on-demand remote snapshot creation for a synchronous replication session between a local system and a remote system of a storage system includes receiving a request for the remote snapshot on the remote system and identifying a current state of the synchronous replication session. The current state is one of a plurality of states. An aspect also includes implementing one or more actions with respect to the remote snapshot as a function of the current state. The actions are performed prior to transitioning from the current state to another state of the plurality of states.