Automated Failover for Paired Consistency Groups During Storage Expansion
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Solution Overview
Problem
Existing multi-site distributed data storage systems face challenges in non-disruptively expanding synchronous data replication relationships while maintaining zero Recovery Point Objective (RPO) and zero Recovery Time Objective (RTO).
Innovation Solution
The system implements an automated failover mechanism that allows for the addition of new storage volumes to existing synchronous data replication relationships without disrupting the zero RPO and zero RTO state. This is achieved through a computer-implemented method that maintains synchronization information, initiates storage expansion processes, and establishes data replication relationships for new volumes while ensuring zero RPO and zero RTO.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If storage expansion is performed during synchronous data replication, then storage capacity is increased, but system stability and data consistency may be compromised
Solution Approach 1:
The system performs preliminary actions by creating new source and destination volumes before expanding the replication relationship. The new volumes are pre-configured and validated, ensuring that the expansion process maintains data consistency from the outset rather than attempting to modify an existing replication relationship mid-operation.
Solution Approach 2:
The expansion process is segmented into distinct phases: creating new source volume, creating new destination volume, and establishing replication relationship. This segmentation allows each step to be independently validated and managed, preventing consistency issues that would arise from attempting a monolithic expansion operation.
2Ease of operation
If manual intervention is required for failover during storage expansion, then operational control is maintained, but recovery time increases
Solution Approach 1:
The system implements self-service through automated failover detection and execution. The replication relationship automatically monitors the health and synchronization status of volumes, and when expansion fails or the primary site becomes unavailable, the system autonomously initiates failover to the destination site without requiring manual intervention, thus minimizing recovery time while maintaining operational integrity.
Solution Approach 2:
The system employs feedback mechanisms where the replication relationship continuously monitors the state of source and destination volumes. This feedback loop enables the system to detect failures during expansion and automatically trigger failover procedures, ensuring rapid recovery while maintaining control through automated decision-making based on real-time system state.
3Reliability
If synchronous replication is maintained during expansion, then data consistency is preserved, but system complexity increases
Solution Approach 1:
The system manages complexity by dynamically changing parameters during the expansion process. The replication relationship is temporarily modified to accommodate new volumes, with parameters such as volume identifiers, replication targets, and synchronization states being adjusted in a controlled sequence. This allows synchronous replication to be maintained while adapting to the expanded configuration without permanently increasing system complexity.
Data Source
AI summary
A computer implemented method includes maintaining information indicative of whether a data replication relationship between a dataset associated with the local CG (CG1) and a mirror copy of the dataset stored on a remote CG (CG2) of a remote distributed storage system is in an in-synchronization (InSync) state or an out-of-synchronization (OOS) state, determining whether a CG storage expansion process is in progress, and in response to determining the OOS state and whether the primary storage site has a failure, initiating an automatic unplanned failover (AUFO) workflow without manual intervention on the original volumes in the CG1 of a first storage cluster of the primary storage site and the original volumes in the CG2 of a second storage cluster when the CG storage expansion process is in progress with a new source volume to be a member of CG1 and a new destination volume to be a member of CG2.