Non-disruptive Storage Volume Migration via Asymmetric Port States
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Solution Overview
Problem
Existing storage volume migration techniques are disruptive, requiring host I/O operations to be interrupted during the migration process, which can lead to downtime and inefficiencies.
Innovation Solution
A method for non-disruptive volume migration between storage controllers, where a migration replication relationship is created to present both the source and target volumes as a single volume to the host, using differentiated target port descriptors to manage I/O operations, allowing seamless switching between them without interrupting host operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If disruptive volume migration techniques are used, then data can be migrated between storage controllers, but host I/O operations must be interrupted causing downtime
Solution Approach 1:
The patent creates a replication relationship between source and target volumes before migration, allowing the target volume to be pre-configured and ready. The host is presented with both the original path and the new path simultaneously, so when switching occurs, the host can immediately access the target volume without interruption. This preliminary preparation eliminates the need for I/O interruption during the actual migration switch.
Solution Approach 2:
The patent introduces a replication relationship as an intermediary mechanism between the source volume and target volume. This replication relationship acts as a bridge that allows seamless data transfer and path switching. The replication relationship manages the coordination between source and target volumes, enabling the host to switch paths without experiencing downtime or I/O interruptions.
2Reliability
If metro mirror relationship is used for volume migration, then data synchronization is achieved, but the host must be reconfigured and I/O must be interrupted
Solution Approach 1:
The patent merges the replication relationship with the path management functionality. By combining these functions, the system can present both source and target paths to the host simultaneously while maintaining data synchronization. The merged mechanism allows the host to see both paths as valid options without requiring manual reconfiguration, as the system automatically manages the switching between paths based on replication status.
3Productivity
If host-based data migration solutions are used, then data can be copied and migrated, but the process requires iterative refresh phases and redirects I/O causing disruption
Solution Approach 1:
The patent replaces the host-based iterative refresh mechanism with a storage controller-based replication system. Instead of the host performing repeated read-write cycles to synchronize data, the storage controllers automatically maintain a replication relationship that continuously synchronizes data in the background. This substitution eliminates the complex iterative refresh phases and automatic I/O redirects that characterize host-based migration solutions.
Data Source
AI summary
A migration replication relationship for data migration between a migration-source volume on a first storage controller and a migration-target volume on a second storage controller, a volume represents a virtualized device. The method presents the migration-source volume and the migration-target volume as a same volume to a host whilst using differentiated target port descriptors to define different discoverable paths to the each. During data migration, the method allows input/output operations to the migration-source volume by presenting target ports of the first storage controller in an available state and deters input/output operations to the migration-target volume by presenting target ports on the second storage controller in a standby state whilst allowing host discovery of paths to the migration-target volume. Once the data migration is complete, the method switches target port states to allow input/output operations to the migration-target volume and to deter input/output operations to the migration-source volume.