Magnetic Disk Drive Sector Indicator for Data Integrity
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Solution Overview
Problem
Magnetic disk drives face challenges in detecting and managing read errors during data block migration, where incorrect data may be returned to the host due to uncorrectable read errors, and there is a need to detect power shutdowns during data block writing.
Innovation Solution
A magnetic disk drive system that embeds an indicator, such as a read uncorrectable bit (UNC) or write count, in each sector data block to indicate the attribute of the sector, allowing for error detection and management without relying on defect management tables, and uses a nonvolatile cache area for temporary storage to ensure data integrity during power shutdowns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If data block migration is performed from first area to second area, then data rewriting capability is improved, but read errors may occur and incorrect data may be returned to host
Solution Approach 1:
The patent applies preliminary action by embedding an indicator (such as a read uncorrectable bit or write count) in each sector data block before writing to the second area. This indicator marks sectors that may contain incorrect data due to read errors during migration, allowing the system to proactively identify and handle potential data integrity issues before they affect data retrieval operations
Solution Approach 2:
The patent uses an indicator bit as an intermediary element between the data migration process and data verification. This indicator serves as a mediator that carries information about read error status from the source sector to the destination sector, enabling the system to track and manage data integrity without requiring complex verification procedures during normal data access
2Ease of operation
If power shutdown occurs during data block write to second area, then system availability is improved, but data loss may occur
Solution Approach 1:
The patent implements feedback by using the indicator embedded in each sector to provide information about the migration status and potential data integrity issues. When power shutdown occurs during migration, the indicator allows the system to identify which sectors may be affected, enabling recovery operations to restore data integrity without requiring complete system reinitialization
Solution Approach 2:
The patent applies preliminary action by pre-marking sectors with indicators that show they are currently being migrated or may contain incorrect data. This preliminary marking allows the system to quickly identify and handle sectors that may be affected by power shutdown, enabling faster recovery and reducing data loss risk
3Difficulty of detecting and measuring
If defect management tables are used to track read errors, then error detection capability is improved, but device complexity increases
Solution Approach 1:
The patent extracts the error detection function from the complex defect management table structure and embeds it directly in each sector data block as an indicator. This extraction eliminates the need for separate management tables and complex lookup operations, reducing device complexity while maintaining error detection capability
Solution Approach 2:
The patent enables self-service by embedding the error detection indicator directly in the sector data block, allowing the sector to carry its own integrity information without requiring external management structures. Each sector becomes self-sufficient in terms of error detection, eliminating the need for centralized defect management tables
Data Source
AI summary
According to one embodiment, a magnetic disk includes a disk, a controller and an indicator module. The disk includes a plurality of data sectors. The controller is configured to control data rewrite for reading a first data block stored in the disk and writing a second data block corresponding to the read first data block to a write destination on the disk. The indicator module is configured to embed an indicator indicative of an attribute relating to data rewrite in each sector data in the second data block written to the write destination when the each sector data is written to the write destination.