Non-Disruptive Virtual Volume Data Migration in Storage Systems
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Solution Overview
Problem
Current data storage systems cannot change the RAID type, layout characteristics, or performance characteristics of virtual volumes while remaining online and accessible to host devices, necessitating a method for non-disruptive modification of these attributes.
Innovation Solution
A system manager in the data storage system maps virtual volumes to logical disk regions and moves data from source to target regions with desired characteristics, mirroring writes, copying data, blocking reads and writes, flushing cache, and updating mappings to ensure the system remains online during these changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If data is moved between logical disk regions to change RAID type or layout characteristics, then the storage system configuration is improved, but the system must go offline causing service disruption
Solution Approach 1:
The patent creates a target logical disk region before moving data, preparing the destination in advance. The system allocates and formats the target region with the desired RAID type and layout characteristics before the actual data migration begins, allowing seamless switching once migration is complete.
Solution Approach 2:
The patent uses an intermediary target logical disk region as a buffer between the source and final destination. Data is copied to this intermediary region while the storage system remains online, then the mapping is switched from source to target, avoiding direct disruption to host devices.
2Adaptability or versatility
If data movement is performed to change virtual volume characteristics, then the storage configuration flexibility is improved, but the data movement time and system load increase
Solution Approach 1:
The patent performs data movement in the background while the storage system continues to serve host devices. The copy operation runs concurrently with normal I/O operations, utilizing idle system capacity and avoiding dedicated downtime for the migration process.
Solution Approach 2:
The patent copies only the necessary portions of data to the target region rather than moving the entire virtual volume at once. The system can switch to the target region progressively as data becomes available, reducing total migration time.
3Reliability
If writes are mirrored to target region during data movement, then data consistency is improved, but the write operation complexity and processing overhead increase
Solution Approach 1:
The patent merges the write operation with the copy operation by directing new writes to both source and target regions simultaneously. This combined approach ensures data consistency without requiring separate mirror operations, reducing overall processing overhead.
Solution Approach 2:
The system establishes write mirroring to the target region before completing the data migration. This preliminary action ensures that from the moment mirroring begins, all new data is captured in both locations, simplifying the consistency maintenance process.
Data Source
AI summary
A method is provided for a data storage system to change the RAID type, the layout characteristics, and the performance characteristics of a virtual volume mapped to logical disk regions in one or more logical disks while the data storage system remains online to a host. Another method is provided for a data storage system to consolidate space in one or more logical disks mapped to a virtual volume while the data storage system remains online to a host. The one or more logical disks can be consolidated to free unused chunklet regions for use in other logical disks.