Magnetic Disk Read Control Seed Verification
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Solution Overview
Problem
In magnetic disk devices, when the scrambler seed expected at the time of read differs from the scrambler seed used at the time of write, existing configurations fail to correctly set the seed value for descrambling, leading to CRC errors and impaired reliability in evaluating read data.
Innovation Solution
The magnetic disk device employs a read control system that generates CRC data for user data extracted from media data, calculates a seed value by performing an XOR operation between the CRC data and the CRC data extracted from the media data, and compares this seed value with the expected seed value. This allows for correct evaluation of read data even if the scrambler seed has changed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the scrambler seed expected at read time differs from the scrambler seed used at write time, then the existing configuration fails to correctly set the seed value for descrambling, but this leads to CRC errors and impaired reliability in evaluating read data
Solution Approach 1:
The patent introduces an intermediary process that extracts the scrambler seed value from the read data itself (embedded in the data field) and uses it as a mediator to perform descrambling. This intermediary approach allows the system to handle cases where the expected seed differs from the actual seed used during writing, by dynamically determining the correct seed from the data rather than relying on pre-stored seed values.
Solution Approach 2:
The patent changes the parameter approach by not fixing the scrambler seed as a predetermined value stored in the controller, but instead allowing the seed value to be dynamically extracted from the read data. This parameter change enables the system to adapt to different seed values used during writing, even when they differ from expected values, thereby preventing CRC errors and maintaining evaluation reliability.
2Measurement precision
If a predetermined scrambler seed is stored in the controller for comparison, then the CRC check can verify data integrity, but the configuration fails when the expected seed differs from the actual seed used at write time
Solution Approach 1:
The patent applies dynamics by transitioning from a static predetermined seed value stored in the controller to a dynamic seed value that is extracted from the read data itself. This dynamic approach allows the CRC check mechanism to adapt to different seed values used during writing, maintaining measurement precision while gaining versatility to handle seed value changes without requiring pre-stored seed information.
Solution Approach 2:
The system performs self-service by extracting the necessary scrambler seed value from the read data itself, rather than relying on external pre-stored seed values in the controller. This self-service mechanism enables the system to independently determine the correct seed for descrambling and CRC verification, providing both accuracy and adaptability without external assistance.
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a read control system that extracts scrambled data from media data read from a medium and inspection data associated with a seed value at the time of write, generates inspection data for data extracted from the media data, obtains from the inspection data and inspection data extracted from the media data, a seed value associated with both, compares this seed value with the seed value expected by the controller, and evaluates, when the comparison result is a mismatch, the data as an error, whereas when match, descrambles the data extracted from the media data using the seed value.