Pruning Free Blocks from Decremental Backup Chains
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Solution Overview
Problem
Decremental backup systems retain unnecessary free blocks, increasing storage size, bandwidth overhead, and processing time during backup and restoration, due to the inclusion of free blocks in successive backups.
Innovation Solution
A method to identify and prune free blocks from a decremental backup chain by creating a master block allocation map from file system block allocation maps and removing free block positions, thereby reducing the size of backups and improving processing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If decremental backup systems retain free blocks in successive backups, then the backup process is simple and fast, but the storage size, bandwidth overhead, and processing time increase significantly
Solution Approach 1:
The patent extracts and removes free blocks from the backup data by comparing block allocation maps across multiple backups. The system identifies blocks that are no longer allocated in the file system and prunes them from the backup chain, reducing the quantity of backup data while maintaining the simplicity and speed of the decremental backup process
Solution Approach 2:
The patent discards free blocks that are no longer needed by the file system from the backup data. By tracking block allocation status across backups and identifying blocks that have been freed, the system recovers storage space and reduces bandwidth requirements by not retaining or transmitting these discarded free blocks
2Device complexity
If free blocks are included in decremental backups, then the backup process is simpler, but the processing time for consolidating and restoring backups increases
Solution Approach 1:
The patent performs preliminary pruning of free blocks from backup data before the consolidation and restoration processes. By proactively removing free blocks using block allocation map comparisons, the system reduces the amount of data that needs to be processed during restoration, thereby reducing processing time without significantly increasing backup process complexity
Data Source
AI summary
Pruning free blocks out of a decremental backup chain. In one example embodiment, a method for pruning free blocks out of a decremental backup in a decremental backup chain includes identifying a decremental backup chain that includes one or more decremental backups of a source storage and a base backup of the source storage, identifying, for pruning, a target decremental backup in the decremental backup chain, retrieving one or more file system block allocation maps (FSBAMs) for points in time represented by the target decremental backup and represented by any of the other decremental backups in the decremental backup chain that depend on the target decremental backup, creating a master block allocation map (MBAM) by combining the one or more FSBAMs, and pruning free blocks, corresponding to block positions that are indicated as being free in the MBAM, out of the target decremental backup.