Journal-Based Data Replication for Storage Systems
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Solution Overview
Problem
Existing data replication technologies between storage systems burden the host computer and communication links, leading to increased operational time, storage capacity requirements, and limitations on distance between storage systems due to inefficient data transfer and replication processes.
Innovation Solution
A data processing system that manages data replication by using journal logical volumes to store update information and write data separately, allowing for asynchronous data transfer and reduced storage capacity needs, while maintaining data consistency through update sequence management and efficient journal handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data replication is performed using existing technologies, then data redundancy is achieved, but the host computer is burdened and communication links are affected
Solution Approach 1:
The patent segments the data replication function from the host computer by introducing a storage system that independently performs replication. The host computer only manages primary storage, while the storage system handles replication to secondary storage, dividing responsibilities and reducing host burden.
Solution Approach 2:
The patent introduces a storage system as an intermediary between the host computer and secondary storage. This intermediary manages the replication process, shielding the host computer from direct involvement in replication operations while ensuring data redundancy.
2Reliability
If synchronous data replication is performed, then data consistency is maintained, but operational time is increased
Solution Approach 1:
The patent implements periodic/asynchronous data replication where the storage system periodically transfers data from primary to secondary storage without requiring real-time synchronization. This periodic action maintains data consistency over time while avoiding the operational delays of synchronous replication.
3Reliability
If large quantity of data is replicated, then comprehensive backup is achieved, but replication time is extended
Solution Approach 1:
The patent performs preliminary actions by maintaining a data structure in the storage system that tracks which data blocks have been replicated. This preliminary tracking allows the system to quickly identify and replicate only the necessary data blocks, reducing overall replication time while ensuring comprehensive backup.
4Reliability
If data replication is performed over long distance, then geographic redundancy is achieved, but update time increases
Solution Approach 1:
The patent uses periodic asynchronous replication to transfer data over long distances. The storage system periodically sends data updates to geographically distributed secondary storage without requiring real-time acknowledgment, achieving geographic redundancy while minimizing the impact of transmission distance on update time.
Data Source
AI summary
A first storage system stores information relating to the updating of data stored in that system as a journal. More specifically, the journal is composed of a copy of data that was used for updating and update information such as a write command used during updating. Furthermore, the second storage system acquires the journal via a communication line between the first storage system and the second storage system. The second storage system holds a duplicate of the data held by the first storage system and updates the data corresponding to the data of the first storage system in the data update order of the first storage system by using the journal.