Shingled Magnetic Recording Verification Method
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Solution Overview
Problem
Shingled magnetic recording (SMR) disk drives face challenges in ensuring data reliability due to the risk of damage from closely packed tracks, necessitating a method to verify data written on adjacent tracks without causing errors.
Innovation Solution
The 'write-squeeze-verify' method, where data in each shingled data track is verified after being written by performing error correction checks or comparing readback data with stored data, incrementing error counters, and allowing re-write attempts to correct errors, with the option to turn off verification if write error frequency is low, and re-formatting regions with high error rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If tracks are packed closely together to increase data density, then storage capacity is improved, but the risk of write errors damaging adjacent tracks increases
Solution Approach 1:
The patent applies preliminary action by performing verification reads immediately after writing each shingled data track. The system reads back the newly written track and adjacent tracks to verify data integrity before proceeding to write the next track, thereby preventing error propagation to adjacent tracks while maintaining high data density
Solution Approach 2:
The patent implements feedback through a verification mechanism that continuously monitors write operations. After each write operation, the system reads back the written data and compares it with the original data to detect write errors. This feedback loop enables real-time detection and correction of errors, ensuring data reliability while maintaining high track density
2Reliability
If verification is performed on every written track, then data reliability is improved, but writing efficiency deteriorates due to additional disk rotation time
Solution Approach 1:
The patent applies partial action by selectively performing verification only on tracks that are likely to contain errors or are critical for data integrity. The system can adjust the verification frequency and scope based on error rates, media conditions, and data importance, thereby balancing reliability requirements with writing efficiency
Solution Approach 2:
The patent implements dynamics through adaptive verification strategies that adjust verification intensity based on real-time error rates and media conditions. When error rates are low, verification frequency is reduced to improve writing efficiency. When error rates increase or media degradation is detected, verification frequency is increased to maintain data reliability
Data Source
AI summary
A “write-squeeze-verify” method is used for verification of the data that has been written in the annular bands of a shingled magnetic recording disk drive. The writing of data along a track overwrites a portion of the previously written track and thus “squeezes” the data of the previously written track to thereby form a “shingled data track” (SDT). The data in each SDT is read back and verified by an error correction check using error correction bits associated with the data written in the SDT, or by comparing the readback data with the data stored in memory. If the data read back is not verified, a write error counter is incremented and a write error frequency is calculated. One or more attempts to write the data can be performed. If the data in the SDT cannot be verified after the attempted rewrite(s), then a “re-try fail” is reported.