Read-Write Snapshot Copy Facility Using Stub Files
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Solution Overview
Problem
Existing data network technologies face challenges in efficiently migrating file data between servers while maintaining concurrent access and balancing storage costs with access delays, particularly in hierarchical storage management systems where snapshot copies are used for data recovery and integrity.
Innovation Solution
A read-write snapshot copy facility is created using stub files with pointers to data files in a read-only snapshot copy, allowing for transparent data access and migration, enabling read-write operations without disrupting concurrent access and facilitating data recovery by promoting the snapshot copy to an independent production file system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a read-only snapshot copy is created of the production file system, then data integrity and recovery capability are improved, but write access and ability to modify data are lost
Solution Approach 1:
The file system is segmented into read-only snapshot copies for integrity preservation and read-write working copies for modification. The system maintains multiple copies at different states, allowing segmentation of functions between them.
Solution Approach 2:
The invention creates read-write copies from read-only snapshot copies by copying data files to stub files in the working copy. This allows the working copy to be modified independently while the snapshot copy preserves the original state for integrity and recovery.
2Productivity
If the entire production file system is duplicated for read-write access, then concurrent access and modification capability are improved, but storage requirements and system complexity increase
Solution Approach 1:
Instead of copying the entire production file system, the invention creates stub files that reference data files in the read-only snapshot copy. Only changed files are copied to stub files, significantly reducing storage requirements while enabling concurrent read-write access.
Solution Approach 2:
The system copies only the necessary changed files from the snapshot copy to the working copy, rather than duplicating the entire file system. This partial copying approach reduces storage overhead while maintaining the required functionality.
3Quantity of substance
If files are migrated from primary to secondary storage for cost reduction, then storage cost is reduced, but access speed and availability deteriorate
Solution Approach 1:
The system dynamically manages file locations by creating stub files that can be promoted to primary storage when needed. Files remain in secondary storage cost-effectively but can be quickly accessed by promoting them to the working copy, providing dynamic adjustment between cost and performance.
Solution Approach 2:
Stub files act as intermediaries between the read-only snapshot copy and the read-write working copy. They enable files to be accessed from secondary storage while maintaining the ability to promote them to primary storage for faster access when needed.
Data Source
AI summary
A read-write snapshot copy facility is constructed from a hierarchical storage management facility. The read-write snapshot copy file system initially comprises stub files pointing to the files in a read-only snapshot copy file system. When an application writes to a file in the read-write snapshot copy, the read-write snapshot copy facility migrates a copy of the file to replace the stub file, and then writes to the migrated file. Because the read-write snapshot copy facility references the files in the read-only snapshot file system in a network namespace using standard protocols such as NFS or CIFS, the read-write snapshot copy facility permits referencing of distributed read-only snapshot file systems in an open (heterogeneous) network environment, and the read-write snapshot copy is scalable by linking the read-write snapshot copy facility to multiple file servers containing read-only snapshot file systems.