Allocation Bitmap for Mounted Volume Cluster Recovery
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Solution Overview
Problem
Current techniques for recovering lost clusters in file systems are inefficient, particularly because they require unmounting the file system and are time-consuming, making it difficult to access data during system failures.
Innovation Solution
The techniques involve generating and modifying an allocation bitmap concurrently with changes to the volume, comparing it to logical allocation structures to identify and recover lost clusters while the file system is mounted, ensuring directory entries and allocation mapping structures remain consistent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current techniques for recovering lost clusters are used, then lost clusters can be recovered, but the file system must be unmounted and the process is time-consuming
Solution Approach 1:
The patent maintains an allocation bitmap that is continuously updated during normal file system operations to reflect the current state of cluster allocations. This preliminary tracking of allocation states allows the system to have recovery information ready before any loss occurs, eliminating the need for time-consuming post-failure analysis. The allocation bitmap is updated concurrently with changes to the volume, ensuring that recovery data is always current without requiring separate scanning operations.
2Reliability
If current techniques for recovering lost clusters are used, then lost clusters can be recovered, but the file system must be unmounted
Solution Approach 1:
The patent enables the file system to remain mounted and operational while continuously maintaining an accurate allocation bitmap that reflects real-time cluster allocation states. The system performs recovery operations by comparing the allocation bitmap with the logical allocation structure while the file system remains accessible, allowing uninterrupted data access during and after recovery processes. This continuous operation eliminates the need to unmount the file system for recovery.
3Productivity
If an allocation bitmap is generated and modified concurrently with volume changes, then lost clusters can be recovered while the file system is mounted, but the system complexity increases
Solution Approach 1:
The allocation bitmap serves multiple functions within the file system: it acts as both a real-time tracking mechanism for cluster allocations during normal operations and as a recovery data structure when losses occur. By designing the bitmap to fulfill both operational monitoring and recovery purposes, the patent reduces the need for separate specialized structures, thereby limiting the increase in overall system complexity while achieving rapid mounted recovery.
Data Source
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AI summary
Techniques for recovering lost clusters are described herein. In particular, this disclosure describes techniques for generating an allocation bitmap. The allocation bitmap may be used to recover lost clusters on a mounted volume.