FAT File System Extent Information Entry for Large File Seeking
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Solution Overview
Problem
The existing FAT file system faces inefficiencies in seeking large files due to the need to follow numerous links, leading to prolonged processing times, and recalculating cyclic shift checksums becomes computationally expensive as file size increases, especially when file data storage area positions and timestamps need to be updated.
Innovation Solution
Implementing an access device with a file system control unit that manages files using extent information entries and a file allocation table, allowing for efficient seeking and checksum recalculation by storing extent information externally and using a cyclic shift checksum for reliability, while separating file types into extensible and normal files for optimized processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the FAT file system follows numerous links to manage large files, then file data can be stored and accessed, but seeking time becomes excessively long and processing speed decreases
Solution Approach 1:
The patent pre-calculates and stores the cumulative byte offsets of all clusters in the extent information entry before file access operations. This preliminary action eliminates the need to sequentially follow FAT links during seeking operations, directly reducing seeking time while maintaining accurate file data management through pre-computed position information.
Solution Approach 2:
The patent segments file management into two parts: the extent information entry that stores pre-calculated cumulative offsets for rapid seeking, and the FAT that maintains cluster link information for data integrity. This segmentation allows seeking operations to use the optimized extent information without being constrained by the sequential nature of FAT link following.
2Reliability
If the cyclic shift checksum is recalculated for all directory entries when file size increases, then data integrity is verified, but computational cost and processing time increase significantly
Solution Approach 1:
The patent segments the checksum calculation into two parts: a first cyclic shift checksum calculated only for extent information entries (which change less frequently), and a second cyclic shift checksum calculated for directory entries (which change more frequently). This segmentation reduces the computational scope for the first checksum, lowering overall processing cost while maintaining data integrity verification through the second checksum.
Solution Approach 2:
The patent performs preliminary checksum calculation on extent information entries separately and stores it in advance. When file operations occur, only the second checksum for directory entries needs recalculation, while the first checksum can be reused or efficiently updated. This preliminary action reduces the computational burden during file operations.
3Ease of operation
If extent information entries are stored in the same area as directory entries, then file management is simplified, but the size of the entry group increases and processing efficiency decreases
Solution Approach 1:
The patent segments storage areas into distinct regions: extent information entries are stored in a separate extent area outside the entry group, while directory entries remain in the entry group. This segmentation prevents the entry group size from increasing due to extent information, maintaining processing efficiency for directory operations while keeping file management straightforward through the separate but linked extent area structure.
Data Source
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AI summary
An information recording device, which includes a nonvolatile memory whose areas are managed using an FAT file system and enhances the reliability of directory entries using a cyclic shift checksum, recalculates the cyclic shift checksum efficiently and performs seeking at a higher speed. A nonvolatile memory (25) of an information recording device 2 is managed using an FAT file system. In the memory, a plurality of directory entries are allocated to a single file. The device enhances the reliability of the directory entries using a cyclic shift checksum, and manages information indicating the position and the size of a storage area of file data using an extent information entry (203). The device further uses an update information entry (204) and a dummy entry (205).