Backup Multi-Link Files via Master File References
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Solution Overview
Problem
Existing file backup and restore systems face challenges in efficiently managing and restoring files with multiple hard links, particularly in maintaining data integrity and reducing duplication during the backup process.
Innovation Solution
The system employs a master file reference approach, where a master file is identified for each multi-link file, and non-master files are mapped to the master file, allowing only the master file to be copied during backup, thus avoiding duplication and preserving the original hard link relationships.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all hard linked files are copied during backup, then data integrity is maintained, but storage space is wasted due to duplication
Solution Approach 1:
Multiple hard linked files are merged into a single master file during backup. The system identifies files that share the same inode number and combines them into one backup entry, eliminating redundant copies while preserving the hard link relationship through metadata storage.
Solution Approach 2:
Instead of copying actual file data for each hard linked file, the system copies only the metadata (inode number, hard link relationships) once. The actual file data is stored as a single copy, and the metadata enables reconstruction of the original hard link structure during restore operations.
2Reliability
If all hard linked files are restored individually, then complete file set is recovered, but restore time increases due to duplication
Solution Approach 1:
The system performs preliminary identification of hard link groups during the backup phase by analyzing inode numbers. This pre-processing organizes files into master-file relationships, so that during restore, the system can directly reconstruct multiple files from a single backup entry without redundant data copying.
Solution Approach 2:
Multiple files that were hard linked are restored as a single unit from one backup entry. The system creates the master file first, then establishes hard link relationships for all associated files, dramatically reducing restore time while ensuring all files are recovered with their original relationships intact.
3Device complexity
If backup system treats each hard linked file as separate, then simplicity is maintained, but efficiency decreases due to redundancy
Solution Approach 1:
The system introduces an intermediary metadata layer that maps backup entries to original hard link relationships. This metadata acts as a mediator between the simplified backup process and the complex hard link structure, allowing the system to treat files as separate during backup while efficiently recognizing and consolidating hard link groups through the metadata.
Data Source
AI summary
Methods and systems for backing up and restoring files that have multiple hard links using master file references and index node-based mappings are described. In some cases, file fetching and restoration may be performed by a storage appliance using master file references in which a master file is identified for each multi-link file that is backed-up on the storage appliance and then referenced by one or more hard links to the multi-link file. In other cases, file fetching and restoration may be performed by a storage appliance using index node-based mappings for multi-link files that provide mappings between index node identifiers (e.g., inode numbers) for the multi-link files on a primary system and hard link paths for storing the file contents of the multi-link files on a storage appliance used for backing up the primary system.