Synchronous Mirror Swap for Storage Failover
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Solution Overview
Problem
Current data storage systems face inefficiencies in swapping synchronous mirror volumes, leading to prolonged recovery times and data inconsistencies when a primary storage volume fails, especially when pre-existing storage relationships are absent.
Innovation Solution
A method and apparatus that activate a synchronous mirror as a primary storage volume by directing updates from a second storage volume to a first storage volume upon the first storage volume's recovery, while maintaining the second, third, and fourth storage volumes in a nearly synchronous state, and establishing new storage relationships without pre-existing relationships.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If synchronous write operations are used to write data to both primary storage volume and mirror storage volume, then data reliability is improved, but write operation time and system overhead increase
Solution Approach 1:
The system dynamically switches between synchronous and asynchronous write modes based on the operational status of storage volumes. When the primary volume is operational, synchronous writes are used for high reliability. When failure occurs, the system transitions to asynchronous writes to the mirror volume to minimize write operation time and maintain productivity.
Solution Approach 2:
The system changes the write operation parameter from synchronous to asynchronous based on system state. This parameter change allows the system to adapt between two extremes: synchronous writes for maximum reliability during normal operation, and asynchronous writes for faster performance during failover scenarios.
2Reliability
If storage volumes are located a long distance from the primary storage volume, then recovery after natural disaster is enabled, but data access rates and performance degrade
Solution Approach 1:
The system segments the storage architecture into local and remote components. The primary storage volume is located locally for high-speed access, while the mirror storage volume is positioned remotely for disaster recovery. This spatial segmentation allows each volume to serve its specific function optimally without compromising the other.
Solution Approach 2:
The system introduces an intermediary mechanism that coordinates between local and remote storage volumes. During normal operation, data is written synchronously to both volumes. Upon failure, the intermediary enables seamless failover by redirecting write operations to the remote mirror volume, maintaining service continuity despite the distance.
3Reliability
If the second storage volume becomes the primary storage volume after the first storage volume fails, then system continuity is maintained, but pre-existing storage relationships may be absent or invalid
Solution Approach 1:
The system performs preliminary actions by pre-configuring the second storage volume as a mirror of the first storage volume before any failure occurs. This preliminary setup ensures that when failure happens, the second volume is already prepared to become the primary volume, eliminating the need to establish storage relationships from scratch and maintaining system continuity.
Solution Approach 2:
Instead of attempting to restore the original primary volume's relationships after failure, the system inverts the approach by making the mirror volume the new primary and establishing fresh relationships. This inversion simplifies the failover process and avoids the complexity of preserving and re-establishing pre-existing relationships.
4Reliability
If the third storage volume continues to receive updates from the second storage volume during failover, then data consistency is maintained, but resynchronization time increases
Solution Approach 1:
The system extracts the third storage volume from the update path during failover scenarios. By stopping updates to the third volume when the first volume fails, the system prevents unnecessary resynchronization work and reduces the time required to restore full functionality, while still maintaining data consistency through the second volume.
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2~3
AI summary
An apparatus, system, and method are disclosed for activating a synchronous mirror as a primary storage volume. The apparatus system and method include directing a third storage volume to store updates sent to the third storage volume from a second storage volume onto a first storage volume in response to the first storage volume becoming operational after a failure, terminating sending updates from the second storage volume to the third storage volume in response to the first storage volume becoming substantially consistent with the third storage volume, and synchronously storing updates received by the second storage volume on the first storage volume and asynchronously storing updates received by the first storage volume on the third storage volume in response to terminating sending updates from the second storage volume to the third storage volume after the first and third storage volumes are substantially consistent.