Shingled Magnetic Recording Off-Track Write Retry Reduction
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Solution Overview
Problem
Shingled magnetic recording (SMR) systems face challenges in reducing off-track write retry operations due to disturbances like vibrations, which lead to decreased throughput and increased power consumption, as the large write element can affect adjacent tracks, causing errors and requiring time-consuming retry operations.
Innovation Solution
The system calculates the percentage of position error signal (PES) at the shingled side end of the initial track and determines if it exceeds a threshold, deciding whether to rewrite data to the same track, an adjacent track, or continue writing to a third track, thereby reducing off-track write retry operations by assessing the combined PES values to determine the probability of data erasure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If shingled magnetic recording is used to increase areal density, then storage capacity is improved, but write operation complexity increases due to the need to rewrite multiple adjacent tracks
Solution Approach 1:
The system performs preliminary actions by pre-calculating PES values and determining the extent of track erasure before actually executing the rewrite operation. This allows the system to prepare the necessary data and determine the scope of work needed, reducing the complexity of the actual write operation execution.
Solution Approach 2:
The patent segments the write operation into distinct phases: reading PES values, calculating erasure probability, determining rewrite scope, and executing the write. This segmentation allows each phase to be handled independently, reducing overall operation complexity.
2Reliability
If off-track write retry operations are performed to correct writing errors, then data accuracy is improved, but throughput decreases and power consumption increases
Solution Approach 1:
The system uses PES (Position Error Signal) feedback to determine whether off-track writing occurred and to calculate the probability of track erasure. This feedback mechanism allows the system to make informed decisions about whether retry operations are necessary, avoiding unnecessary retries that would reduce throughput and increase power consumption.
Solution Approach 2:
Instead of always performing full retry operations, the system applies partial action by only rewriting tracks when the calculated erasure probability exceeds a threshold. This selective approach maintains data accuracy while minimizing the impact on throughput and power consumption.
3Reliability
If off-track write retry operations are performed to correct writing errors, then data accuracy is improved, but time consumption increases
Solution Approach 1:
The system performs preliminary calculation of erasure probability using PES values before executing retry operations. This preliminary assessment allows the system to quickly determine whether a retry is needed, reducing the time spent on unnecessary retry operations while maintaining data accuracy.
Solution Approach 2:
The system applies partial retry operations only when necessary, based on the calculated erasure probability. By avoiding full retry operations when they are not needed, the system maintains data accuracy while significantly reducing time consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves drive performance, reduces power consumption, and extends hardware lifespan by minimizing mechanical movement and retry operations, especially in environments with disturbances like vibrations.
Implementation Method 1
a write element with a write width that is larger than a defined track pitch
Implementation Method 2
a strong write field gradient is needed to shift the polarity of cells on a magnetized medium
Data Source
AI summary
Methods and systems that reduce off-track write retry operations in shingled magnetic recording systems. In one implementation, the method includes writing data to an initial track, determining which side of the initial track is a shingled side, calculating a percentage of position error signal (PES) at a shingled side end of the initial track (PES1) when an off-track write operation occurs, determining whether the PES1 meets a first pre-determined threshold, continue writing data to a second track responsive to determining the PES1 is below a first pre-determined threshold, calculating a percentage of PES at a shingled side end of the second track (PES2), determining whether a combined value of PES1 and PES2 is above a second predetermined threshold to determine a probability value of the initial track being erased, and continue writing to a third track if the combined value is below the second predetermined threshold.