Remote Copy System Time-Ordered Data Consistency
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Solution Overview
Problem
Existing remote copy systems face challenges in ensuring data consistency and ordering across multiple storage apparatuses or volume groups, particularly during disasters, leading to potential data loss and disruptions in business operations.
Innovation Solution
A remote copy system that associates volume groups for remote copying with those for backup, using time ordering to maintain data consistency across separated groups, and allocates high-capacity storage to journal volumes for continuous remote copying and replica creation, even during journal data restoration suspension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If asynchronous remote copy is used to improve host system response performance, then the host system does not need to wait for remote I/O completion, but data consistency and ordering cannot be guaranteed across multiple storage apparatuses or volume groups during disasters
Solution Approach 1:
The system divides storage resources into separate volume groups (primary volume group for host I/O operations and secondary volume group for backup operations). This segmentation allows independent operation of each group while maintaining overall consistency through the backup relationship, resolving the contradiction between performance and reliability.
Solution Approach 2:
The backup volume group acts as an intermediary between the primary volume group and the final backup destination. It receives data from the primary volume group and maintains time-ordered consistency, serving as a mediator that ensures data ordering without requiring synchronous operations.
2Quantity of substance
If data is handled across multiple storage apparatuses or volume groups to increase capacity, then the system can handle enormous data volumes, but consistency of data ordering cannot be guaranteed during disaster recovery
Solution Approach 1:
The system merges multiple volume groups into a unified backup structure where the backup volume group coordinates data from multiple primary volume groups. This merging ensures that time ordering consistency is maintained across all volume groups through a centralized backup management mechanism.
Solution Approach 2:
The system performs preliminary backup operations to the backup volume group before actual disaster recovery. By preparing and validating data ordering consistency in advance during normal operations, the system ensures that time ordering is maintained even when handling data across multiple storage apparatuses.
3Reliability
If synchronous remote copy is used to guarantee data writing completion at remote site, then data consistency is ensured, but host system response performance deteriorates due to waiting for remote I/O completion
Solution Approach 1:
The system performs preliminary data transfer to the backup volume group asynchronously, then validates consistency in advance. This preliminary action allows the host system to continue operations without waiting for synchronous confirmation, while still guaranteeing data consistency through the backup relationship.
Solution Approach 2:
The backup volume group continuously maintains the ability to restore data even when primary storage fails. This continuous backup capability ensures data reliability without interrupting host system operations, as the backup process runs independently and continuously.
Data Source
AI summary
Provided is a remote copy system capable of guaranteeing the time ordering of data to be handled by a remote site even when the tasks at the remote site are operated across a plurality of storages or a plurality of volume groups. A consistency group consisting of a secondary journal volume and a replica is associated with a journal group consisting of a primary data volume, a primary journal volume, a secondary journal volume, and a secondary data volume. Upon backing up a secondary data volume and forming a replica, the host system issues a backup time reservation command to a storage apparatus, and the storage apparatus creates a replica by comparing the time stamp added to the journal data and the backup reservation time.