Asynchronous Remote Copy Data Consistency via Differential Journal Transfer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In asynchronous remote copy systems, when the first storage apparatus is terminated, the operation is not continued appropriately due to discrepancies in update numbers between the second and third storage apparatuses, leading to data being copied from an older status to a newer status, which can occur during failures or planned shutdowns.
Innovation Solution
The system determines which storage apparatus has the newer update number and transfers differential journals from the newer to the older apparatus, ensuring data consistency by reflecting these journals in the appropriate data volumes in ascending order of update numbers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If asynchronous remote copy is implemented with multiple copy destinations, then data redundancy and reliability are improved, but data consistency and update number synchronization deteriorate when the first storage apparatus is terminated
Solution Approach 1:
The system performs preliminary actions by having the second and third storage apparatuses continuously track and record update numbers from the first storage apparatus before termination occurs. This allows the system to quickly determine which apparatus has the newer data state after termination, enabling proper resynchronization without manual intervention or data inconsistency.
2Manufacturing precision
If all journals are transferred from the newer storage apparatus to the older one after termination, then data consistency is restored, but transfer time and system downtime increase
Solution Approach 1:
The system extracts only the necessary differential journals from the newer storage apparatus (second or third) that are needed to synchronize the older apparatus, rather than transferring all journals. This is achieved by comparing update numbers and identifying only the missing range, significantly reducing transfer time and downtime while maintaining data consistency.
3Manufacturing precision
If the system waits for complete journal transfer before resuming operations, then data integrity is ensured, but operational continuity and productivity decrease
Solution Approach 1:
The system performs partial action by transferring only the essential differential journals needed for synchronization rather than waiting for complete journal transfer. The update number comparison mechanism allows the system to identify and transfer only the minimum necessary data range, enabling operations to resume faster while maintaining data integrity through the journal reflection process.
Data Source
AI summary
In a previous storage apparatus, differential JNLs are reflected in order of the sequential numbers, to the data volumes thereof. If a first storage apparatus is suspended, it is determined which is newer: the sequential number which the journal recently reflected in a second storage apparatus or the sequential number reflected in a third storage apparatus. In the newer storage apparatus having the newer sequential number, it is determined whether one or more JNLs from the journal having the sequential number next to the sequential number which is not determined to be the newer to the journal having the sequential number determined to be the newer exist, or not. If the result of the determination is positive, from the newer storage apparatus to the previous storage apparatus which is not the newer of the second and the third storage apparatuses, one or more differential JNLs are copied.