Storage Replication Consistency Across Snapshot and Continuous Modes

The patent introduces a consistency group as an intermediary structure that manages multiple volumes replicated in different modes. The consistency group coordinator acts as a mediator to coordinate snapshot operations across all volumes, ensuring that despite different replication modes, all volumes reach a consistent state at designated points in time. This resolves the contradiction by allowing mode flexibility within volumes while maintaining overall consistency through the intermediary coordination layer.

The patent segments the replication system into distinct consistency groups, where each group can be managed independently with its own coordination mechanism. This allows continuous replication to be applied selectively to critical volumes that require high reliability, while less critical volumes can use simpler snapshot shipping modes. The segmentation reduces overall system complexity by isolating the complex continuous replication logic to only where it's needed, rather than requiring it across all volumes.

The patent implements periodic snapshot shipping at scheduled intervals for non-critical volumes, which efficiently utilizes storage resources by not continuously replicating all data. The periodic action is complemented by consistency group coordination that ensures these periodic snapshots are synchronized with other volumes at key recovery points. This approach balances storage efficiency with retrieval timeliness by using periodic updates rather than continuous transmission, while the consistency coordination minimizes the time loss through organized recovery procedures.