Hash-Based Backup Link Map for Defragmentation Overhead
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Solution Overview
Problem
Conventional backup methods incur unnecessary overhead due to the need for complete backups after defragmentation, as the backup software perceives changes in file locations rather than content, preventing incremental backups and inefficiently using storage resources, especially in server environments with frequently updated software.
Innovation Solution
A method utilizing hash functions to identify and link blocks with identical contents, allowing for efficient backup and restoration by generating hash values for each block, creating a map of links, and modifying links during defragmentation to point to the same backed-up block, thereby reducing redundant backups and optimizing storage usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional backup methods are used after defragmentation, then complete backup must be performed to ensure data integrity, but backup overhead and storage resource usage increase significantly
Solution Approach 1:
The system performs preliminary hashing of all data blocks before backup, creating a hash map that records the original position and hash value of each block. This preliminary action enables the backup system to quickly identify unchanged blocks after defragmentation by comparing hash values, avoiding the need for complete re-backup and significantly reducing backup overhead while maintaining data integrity.
Solution Approach 2:
The patent replaces the mechanical block-by-block verification process with a hash-based identification system. Instead of physically comparing each data block during backup, the system uses cryptographic hash functions to generate unique identifiers for each block. This substitution transforms the backup verification from a time-consuming mechanical process into a rapid computational comparison, dramatically reducing backup time and resource consumption.
2Productivity
If incremental backup is performed based on file location changes, then backup efficiency improves, but data accuracy deteriorates due to false detection of changed blocks
Solution Approach 1:
The patent introduces hash values as an intermediary between the physical block location and the logical data content. The hash map serves as a mediator that decouples the relationship between block position and data identity. When a block is moved during defragmentation, the hash value remains unchanged, allowing the system to accurately identify that the data content is unchanged despite the location change, thus improving both backup efficiency and change detection accuracy.
Solution Approach 2:
The system changes the parameter used for identifying data blocks from physical location (block address) to content-based identification (hash value). This parameter transformation allows the backup system to ignore location changes and focus on actual content changes. By comparing hash values rather than block addresses, the system achieves accurate change detection while maintaining high backup efficiency through incremental backups.
Data Source
AI summary
A method, system and computer program product for data backup such that: for each block of a storage device to be backed up to an image, generating a hash function value corresponding to contents of that block; generating a map of links between blocks in the image and corresponding blocks the storage device; using the hash function values to identify blocks of the storage device with identical contents, such that links for the blocks in the storage device with identical contents point to a single block in the image; and modifying the link in the map when a block in the storage is moved (for example, due to defragmentation) but its contents is not altered, so that the link points to the same backed up block.