Large Range Defect Allocation in Data Storage
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Solution Overview
Problem
Existing defect reallocation schemes in data storage devices, such as hard disk drives, are inefficient for large range defects as they require numerous extra read/write and verification operations, are limited by sector-by-sector reallocation, and increase memory costs, leading to slowed operation and user dissatisfaction.
Innovation Solution
A dynamic remapping scheme that reallocates large range defects by identifying defect ranges, moving data to a reserve area, and updating logical address tables, reducing memory usage and maintaining drive performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sector-by-sector reallocation is used for defect management, then comprehensive defect coverage is achieved, but operation speed decreases and memory costs increase
Solution Approach 1:
The patent segments defect management into two distinct approaches: traditional sector-by-sector reallocation for small defects, and a new large-range defect reallocation method for extensive defects. This segmentation allows each method to be optimized independently, with the large-range method using range-based identifiers instead of individual sector entries, thereby reducing memory usage and improving operation speed while maintaining comprehensive defect coverage.
Solution Approach 2:
The patent introduces a new dimension to defect management by transitioning from one-dimensional sector-by-sector tracking to two-dimensional range-based tracking. The large-range defect reallocation uses start sector identifiers and length fields to define defect ranges, creating a hierarchical structure that combines both detailed sector-level tracking and efficient range-level management, thus resolving the contradiction between comprehensive coverage and operational efficiency.
2Reliability
If traditional defect reallocation tables are used, then all defects can be tracked, but memory requirements increase
Solution Approach 1:
The patent merges the functionality of multiple separate tables (defect identification table and reallocation table) into a unified large-range defect reallocation table. This merged table stores defect range information, allocation information, and verification status in an integrated structure, reducing the total memory footprint while maintaining complete defect tracking capabilities through efficient data organization.
Solution Approach 2:
Instead of storing individual sector defect information and then grouping them, the patent inverts the approach by first defining defect ranges and then managing individual sectors within those ranges. The table stores range-level metadata (start sector, length, allocation status) that automatically covers all sectors within the range, thereby tracking completeness with minimal memory usage.
3Measurement precision
If numerous read/write and verification operations are performed for large range defects, then reallocation accuracy is improved, but operation time increases
Solution Approach 1:
The patent applies preliminary action by performing verification operations during the data migration process itself. The verification bit is set during the reallocation operation, confirming that data was successfully moved to the new location. This eliminates the need for separate post-reallocation verification passes, maintaining reallocation accuracy while reducing total operation time.
Solution Approach 2:
The patent ensures continuity of useful action by integrating multiple functions into a single continuous operation. The large-range defect reallocation performs data identification, data migration, and verification in one continuous process rather than separate discrete operations. This continuous approach maintains accuracy through built-in verification while minimizing operation time by eliminating idle periods between steps.
Data Source
AI summary
A method includes moving data in a defect range from a defective area of a data storage medium to a reserve area of the data storage medium, and identifying the defect range by an address of a start of the defect range and a defect length. A logical address table is updated with the address of the start of the defect range, the defect length and an offset to the reserve area.