Journal-Based Replication for Asynchronous Copy on Write
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Solution Overview
Problem
Conventional data protection systems face challenges in maintaining continuous data protection by keeping pace with high data transaction rates at production sites, leading to potential shutdowns due to backlog of un-logged transactions at backup sites.
Innovation Solution
A method and system that utilize a journal-based replication appliance to create asynchronous copies and cache writes, allowing for efficient data recovery and synchronization between production and backup sites by using a virtual image data structure and caching mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If synchronous journaling is used to maintain continuous data protection, then data reliability is improved, but production site performance deteriorates due to the overhead of requiring several data transactions at the backup site for each production site transaction
Solution Approach 1:
The patent segments the journaling process into two independent parts: (1) production site writes data to its local journal without waiting for backup confirmation, and (2) backup site receives and processes journal data asynchronously. This segmentation removes the blocking relationship between production and backup operations, allowing high transaction rates at the production site while maintaining data protection continuity through the segmented journaling architecture.
Solution Approach 2:
The patent introduces an intermediary mechanism where the production site writes to a local journal first, which then serves as a buffer and intermediary for the backup site to process data asynchronously. This intermediary journal allows the production site to continue operations without waiting for backup confirmation, while the backup site can process data at its own pace, resolving the contradiction between reliability and productivity.
2Stability of the object's composition
If backup site processes all journal data before production site can write, then data consistency is improved, but system downtime increases during recovery operations
Solution Approach 1:
The patent applies preliminary action by having the production site write to its journal in advance before the backup site processes the data. The journal data is prepared and staged at the production site first, then transferred and applied at the backup site asynchronously. This preliminary journaling at the production site eliminates the need to wait for backup processing before writing, reducing recovery downtime while maintaining consistency through the journal's ordered sequence.
Solution Approach 2:
The patent ensures continuity of useful action by allowing the production site to continue writing to its journal without interruption while the backup site processes data continuously in the background. Both operations proceed simultaneously and independently, with the journal serving as the continuous record that maintains data consistency without forcing the production site to stop for backup operations.
3Productivity
If asynchronous copy on write is implemented, then write performance is improved, but data synchronization complexity increases
Solution Approach 1:
The patent uses copying by creating a journal copy of the production site's data changes. Instead of directly synchronizing production data to the backup site in real-time, the system creates a copy of the changes in the journal, which is then transferred and applied asynchronously. This copying mechanism simplifies synchronization by decoupling the write operation from the synchronization operation, improving write performance while managing complexity through the journal copy.
Data Source
AI summary
A method, system, and computer program product for receiving a request to roll an image to a point in time by reading data from a journal, applying data from the journal to create a asynchronous copy on write image at the requested point in time, creating a virtual image data structure, and allowing writes to be cached in a journal based replication appliance.