Open File Backup via Write Interception and Change Logging
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Solution Overview
Problem
Traditional backup systems cannot effectively back up open and locked data files, such as e-mail and database files, due to exclusive access locks, frequent changes, and transaction inconsistencies, leading to incomplete or inconsistent backups.
Innovation Solution
A method that intercepts and delays write operations to an open data file, records the address ranges of these operations in a change log, and creates a consistent backup by copying the file's contents and applying changes after the backup file is updated, allowing for snapshot creation during quiescent periods, thus bypassing the exclusive access lock and ensuring file consistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If standard backup applications attempt to copy locked data files, then backup capability is improved, but the exclusive access lock prevents access and backup fails
Solution Approach 1:
The patent introduces a file system filter driver as an intermediary component positioned between the owning application and the file system. This filter driver intercepts write operations to the data file, allowing the backup application to access and copy the file contents while the owning application maintains its exclusive lock. The intermediary enables simultaneous read access for backup and locked write access for the application without direct conflict.
Solution Approach 2:
The patent segments the write operation handling by separating the interception function (performed by the file system filter driver) from the actual write execution. Write operations are intercepted, processed, and forwarded in a segmented manner that allows the backup application to read file contents between interception points, enabling backup while maintaining application access.
2Quantity of substance
If multiple read operations are used to copy large files, then backup of large files is improved, but file changes during copying result in inconsistent backups
Solution Approach 1:
The patent implements preliminary action by having the file system filter driver pre-intercept and queue write operations before they are executed. Before the backup application performs its read operations, the filter driver has already captured information about upcoming write operations, allowing it to manage the copying process in a way that ensures consistency even for large files copied through multiple read operations.
Solution Approach 2:
The patent establishes a feedback mechanism where the file system filter driver continuously monitors and intercepts write operations, providing real-time information about file changes. This feedback allows the backup process to adjust its reading and copying operations accordingly, ensuring that the backup reflects a consistent state of the file even when the file is being modified during the backup process.
3Productivity
If volume snapshots are performed periodically, then backup frequency is improved, but snapshots can occur in the middle of transactions producing inconsistent copies
Solution Approach 1:
The file system filter driver acts as an intermediary that sits between the volume snapshot mechanism and the actual file system operations. It intercepts and monitors write operations, including those occurring during transactions, and manages the snapshot process to ensure consistency. The intermediary enables frequent snapshots while preventing inconsistent copies by coordinating with the transaction processing.
Solution Approach 2:
The patent replaces the mechanical approach of taking raw volume snapshots with a software-based filtering and interception mechanism. Instead of directly copying file contents at arbitrary points, the file system filter driver uses software hooks to intercept and manage write operations, substituting the simple mechanical snapshot approach with a more sophisticated software-controlled process that ensures transaction consistency.
4Stability of the object's composition
If journal files are created to log all data changes, then backup consistency is improved, but additional write operations impact application performance
Solution Approach 1:
The patent extracts the write interception and logging function from the application's normal operation flow and places it in the file system filter driver. By taking out this function and implementing it at the file system level, the application itself does not need to perform additional write operations for logging, thus maintaining backup consistency without impacting application performance. The filter driver handles the interception transparently.
Solution Approach 2:
The file system filter driver provides self-service by automatically intercepting, logging, and managing write operations without requiring application involvement. The driver handles the entire process of capturing write information, managing the change log, and coordinating with backup operations autonomously, eliminating the need for the application to perform additional operations that would impact its performance.
Data Source
AI summary
A method for backing up a computer-readable data file with a computerized backup application, where the data file is open and locked for exclusive access by an owning application that is mutually independent of the backup application. The backup application by-passes the lock on the data file. Any write operations to the data file by the owning application are intercepted and delayed. The address range of any write operations directed to the data file by the owning application during the backup procedure are written to a change log file, where the change log file contains no indication of the content of the write operations. At least a portion of the data file is copied to a backup file, and any intercepted and delayed write operations are passed on to the data file after the data to be overwritten has been copied to the backup file.