Data Migration Using Invalid Bits for Non-Disruptive Volume Remapping
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Solution Overview
Problem
Existing data migration techniques in computer systems often require stopping and restarting applications, which is undesirable due to application usage requirements and regulatory constraints, and they do not allow for transparent and non-disruptive data migration between logical volumes with different data protection levels or physical storage characteristics.
Innovation Solution
A method for data migration that involves identifying a source and target logical volume, configuring the target if necessary, setting invalid bits to indicate data inconsistencies, and copying data while maintaining continuous I/O operations without interrupting replication services, using a temporary storage area to remap physical storage areas and ensure data consistency across different RAID groups with varying protection levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data migration is performed using traditional techniques, then data can be copied from source to target volume, but application I/O operations must be stopped and restarted causing service interruption
Solution Approach 1:
The patent applies preliminary action by configuring the target logical volume with appropriate mirror settings and data protection levels before initiating the data migration process. This preparation ensures that the target volume is ready to receive data without interrupting application I/O operations on the source volume, thereby maintaining application availability while ensuring migration completeness
Solution Approach 2:
The patent introduces an intermediary mechanism through invalid bits that mediate between the source and target volumes during migration. These invalid bits track which data portions have been copied, allowing the system to manage the migration process continuously without stopping application operations, thus resolving the contradiction between migration reliability and application availability
2Adaptability or versatility
If data migration is performed between volumes with different data protection levels, then storage flexibility is improved, but data consistency and integrity become more difficult to maintain
Solution Approach 1:
The patent applies local quality by allowing different data protection levels and mirror configurations at different locations (source volume, target volume, and intermediate mirrors) within the same migration system. Each volume can have its own protection level appropriate to its role, providing storage flexibility while maintaining data consistency through the invalid bit tracking mechanism that ensures complete data transfer regardless of protection level differences
Solution Approach 2:
The patent utilizes parameter changes by allowing the data protection level parameter to vary between source and target volumes during migration. The system dynamically adjusts to these parameter differences by using invalid bits to track data portions that need to be copied, ensuring data consistency is maintained even when migration occurs between volumes with different protection levels and storage characteristics
3Ease of manufacture
If the source volume is made unavailable during migration, then data copying can be performed, but application usage and regulatory requirements are violated
Solution Approach 1:
The patent implements continuity of useful action by enabling data migration to proceed continuously in the background while application I/O operations continue uninterrupted on the source volume. The invalid bit mechanism allows the system to track and complete data copying without requiring the source volume to be taken offline, thereby maintaining both copying effectiveness and application continuity
Solution Approach 2:
The invalid bit serves as an intermediary that enables the system to manage data copying simplicity while maintaining application continuity. By tracking which data portions have been copied through these bits, the system can perform migration without interrupting applications, resolving the contradiction between copying simplicity and operational ease
Data Source
AI summary
Described are techniques for performing data migration for a source logical volume and a target. The target is configured as storage for another mirror of the source logical volume prior to copying data from the source logical volume to the target, and if the target is configured storage of another logical volume of the data storage system, the configured storage is remapped as storage for another mirror of the source logical volume prior to copying data from the source logical volume to the target. One or more invalid bits are set indicating that the target does not contain a valid copy of data from the source logical volume. Data is copied from the first mirror of the source logical volume to the target. Invalid bits are cleared as data portions of the first mirror of the source logical volume are copied to the target.