Storage Subsystem Migration Without Internal Volume Copying
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Solution Overview
Problem
Existing storage system migration techniques require creating internal volumes of equal capacity, leading to elongated migration time and deteriorated response performance due to the need for double data copying between external and migration destination storage subsystems.
Innovation Solution
A storage system with a migration source and destination subsystem, along with an external subsystem, utilizing cache memories to associate and allocate volumes virtually, allowing direct data transfer and eliminating the need for internal volume creation and double copying, while ensuring continuous IO access through cache duplication and path switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If internal volumes are created in the migration destination storage subsystem and double data copying is performed (from external storage to migration destination and back), then data migration can be achieved, but migration time is elongated and response performance is deteriorated
Solution Approach 1:
The patent extracts and eliminates the unnecessary intermediate step of creating internal volumes in the migration destination storage subsystem. By directly connecting the external storage subsystem to the migration destination and performing single-copy migration, it removes the redundant data copying process that was causing time loss, while still achieving complete data migration through direct external volume mapping.
Solution Approach 2:
Instead of the conventional approach of migrating data through internal volumes (external → migration destination internal → external), the patent inverts the migration path by directly mapping external volumes to the migration destination storage subsystem. This reversal eliminates the double-copying process and reduces migration time while maintaining data integrity.
2Reliability
If internal volumes of equal capacity are prepared in the migration destination storage subsystem, then data migration can proceed, but storage resources are consumed and device complexity increases
Solution Approach 1:
The patent removes the requirement to create internal volumes in the migration destination storage subsystem. By directly mapping external volumes to the destination, it eliminates the complex volume creation and capacity matching process, reducing device complexity while ensuring complete data migration through direct external volume association.
3Productivity
If data is transferred directly from migration source to external storage during migration, then response performance improves, but data consistency during migration may be compromised
Solution Approach 1:
The patent introduces the migration destination storage subsystem as an intermediary that receives write requests from the host computer during migration. This mediator ensures data consistency by routing all writes through the destination subsystem, which then synchronizes with the external storage, maintaining data integrity while allowing continued I/O operations during migration.
Data Source
AI summary
The present invention provides a storage system capable of performing data migration without stopping the IO access from a host computer, without having to copy data in an external connection storage subsystem to a migration destination storage subsystem. A configuration information of a migration source volume in a migration source storage subsystem is migrated to the migration destination storage subsystem, and during migration, cache memories of the respective subsystems are used to duplicate and store write data from the host computer, and the migration destination storage subsystem reflects the write data to the external connection storage subsystem. Reading of data is also performed by the migration destination storage subsystem.