Asynchronous Storage Snapshot via Journal Marker
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Solution Overview
Problem
In asynchronous remote copy systems, creating a backup of a primary site at a specific time point on a secondary site is challenging due to the asynchronous nature of data replication, which complicates data synchronization and recovery processes.
Innovation Solution
A storage system is configured with a first and second storage apparatus, where the first storage apparatus creates a data volume and journal volume, transfers journal updates to the second storage apparatus, and upon detecting a specific condition, the second storage apparatus creates a snapshot of the data volume, enabling efficient backup and recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If asynchronous remote copy is used to transfer data between storage apparatuses, then response time to write commands is improved, but the ability to create accurate time-point backups deteriorates
Solution Approach 1:
A journal volume is introduced as an intermediary component between the data volume and the backup system. The journal records all data changes in chronological order, allowing the backup system to reconstruct accurate time-point snapshots by processing journal entries sequentially, thus resolving the conflict between fast asynchronous copying and precise time-point backup capability
Solution Approach 2:
The system performs preliminary actions by continuously writing data changes to the journal volume before actual backup operations. This preliminary recording of all modifications enables the backup system to accurately reconstruct any point-in-time state without requiring synchronous data capture, thereby maintaining both fast response times and precise time-point accuracy
2Reliability
If synchronous remote copy is used to maintain constant data synchronization, then data consistency is improved, but response time to write commands deteriorates
Solution Approach 1:
The data replication process is segmented into two independent components: a journal volume that records all changes locally with immediate acknowledgment to hosts, and a data volume that is updated asynchronously from the journal. This segmentation allows the system to maintain data consistency through the journal while providing fast response times independent of remote copy operations
3Loss of time
If asynchronous remote copy is used between sites separated by large distances, then response time is improved, but the complexity of creating time-point backups increases
Solution Approach 1:
The journal volume serves as a mediator that simplifies the backup creation process. By continuously recording all data changes in a structured format, the journal provides a straightforward mechanism for reconstructing any time-point backup without complex coordination or synchronization protocols, thereby reducing backup creation complexity while maintaining fast asynchronous copy performance
Data Source
AI summary
In order to create, at another site, a backup of a volume at a specific time point while minimizing the response time required to update the volume, a first storage apparatus and a second storage apparatus transfer a journal in a first journal volume to the second storage apparatus, the second storage apparatus writes the transferred journal into a second journal volume, the second storage apparatus reads journals in the second journal volume in order of the update, the second storage apparatus reflects the read journals to a second data volume, the first storage apparatus creates, in the first journal volume, a journal including a marker when a specific condition is satisfied, and the second storage apparatus creates a snapshot of the second data volume upon detecting a marker in the read journal.