Masterless Backup of Multi-Link Files via Inode Mapping
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Solution Overview
Problem
Existing file backup and restoration systems face challenges in efficiently managing and restoring files with multiple hard links, particularly in identifying and handling master files, which can lead to data duplication and complexity in maintaining file relationships.
Innovation Solution
The implementation of index node-based mappings allows for the identification of a master file for multi-link files, enabling efficient backup and restoration by storing only one copy of the master file and maintaining pointers for non-master files, thereby avoiding data duplication and preserving original file relationships.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional backup systems backup each hard link as a separate file, then all file references are preserved, but data duplication occurs and storage efficiency decreases
Solution Approach 1:
The patent merges multiple hard links pointing to the same inode into a single backup entry. The backup system identifies that multiple files (hard links) share the same inode number and file content, then stores only one copy of the actual file data while maintaining references to all original file paths. This combining approach eliminates redundant data storage while preserving the complete file reference structure.
Solution Approach 2:
The patent creates a universal backup entry structure that handles both single-link and multi-link files uniformly. The backup system uses a single data structure format that can represent any file reference, whether it's a unique file or one of multiple hard links to the same inode. This multi-functional approach allows the system to manage diverse file reference types through a consistent mechanism, improving both storage efficiency and reference preservation.
2Quantity of substance
If master files are identified and tracked for multi-link files, then data duplication is reduced, but system complexity increases
Solution Approach 1:
The backup system performs self-service by automatically identifying master files through inode number analysis without requiring manual intervention or complex external management. The system scans the file system, groups hard links by their inode numbers, and autonomously determines which file to treat as the master (typically the first encountered or alphabetically first). This self-service approach minimizes the need for additional management infrastructure while achieving deduplication goals.
Solution Approach 2:
The patent introduces an intermediary metadata structure that acts as a mediator between the file system and backup storage. This intermediary layer stores the mapping relationships between multiple file paths and their corresponding inode numbers, allowing the backup system to efficiently identify and consolidate duplicate files without directly complexifying the underlying file system management. The metadata structure serves as a buffer that simplifies the deduplication process.
3Reliability
If all hard links are backed up as separate files, then complete file restoration is possible, but backup size and transfer time increase
Solution Approach 1:
The backup system merges multiple hard link references into a single backup operation by identifying shared inodes. When multiple files point to the same inode, the system performs one backup transfer for that inode rather than separate transfers for each file path. This merging significantly reduces total backup transfer time while maintaining the ability to restore any individual file reference, as the restoration process can recreate hard links from the shared backup data.
4Quantity of substance
If index node-based mappings are implemented, then storage efficiency improves, but implementation complexity increases
Solution Approach 1:
The patent uses index node (inode) numbers as an intermediary key to organize and manage file deduplication. Rather than directly comparing entire file contents or maintaining complex file tree structures, the system leverages the inode number as a unique identifier that naturally groups hard links. This intermediary approach simplifies the mapping complexity by providing a straightforward key-based organization method that efficiently achieves storage efficiency goals without requiring elaborate implementation structures.
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.