Shingled Magnetic Recording Guard Band Assignment for Localized ATI Protection
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Solution Overview
Problem
Data Storage Devices (DSDs) face issues with Adjacent Track Interference (ATI) and Wide Area Track Erasure (WATER) due to increased areal density and the use of stronger magnetic fields or energy-assisted recording techniques, leading to data corruption and reduced storage capacity when guard bands are widened to mitigate these issues.
Innovation Solution
Assigning localized guard band sectors from adjacent tracks based on Magnetic Recording Metrics (MRM) to protect data from ATI and WATER without significantly reducing storage capacity, by identifying susceptible areas and designating sectors for guard bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If guard band width is increased to protect data from ATI and WATER, then data integrity is improved, but storage capacity is reduced
Solution Approach 1:
The patent applies local quality by assigning guard band sectors selectively based on susceptibility to ATI and WATER. Instead of uniformly increasing guard band width across the entire disk surface, the system identifies specific annular locations and tracks that are more susceptible to interference and assigns guard band sectors only to those locations. This localized approach protects vulnerable data regions while preserving storage capacity in less vulnerable regions.
Solution Approach 2:
The patent segments the guard band protection into discrete sectors assigned from adjacent tracks. Rather than creating continuous wide guard bands that consume significant space, the system divides protection into individual sectors that can be selectively assigned. This segmentation allows fine-grained control over where protection is applied, enabling the system to protect only the specific sectors that are susceptible to interference while leaving other sectors available for data storage.
2Quantity of substance
If narrower tracks are used to increase TPI in SMR, then areal density is improved, but track interference (ATI and WATER) worsens
Solution Approach 1:
The patent addresses track interference by applying local quality through selective guard band sector assignment. Instead of uniformly increasing track spacing or reducing areal density across the entire disk, the system identifies specific tracks and annular locations where ATI and WATER are more severe and assigns guard band sectors only to those locations. This allows the system to maintain narrow tracks for high areal density while providing targeted protection against interference in vulnerable regions.
3Quantity of substance
If energy-assisted recording techniques are used to write smaller tracks, then areal density is improved, but susceptibility to ATI and WATER increases
Solution Approach 1:
The patent applies local quality by selectively assigning guard band sectors to regions that are more susceptible to interference from energy-assisted recording techniques. The system identifies specific tracks and annular locations where HAMR or MAMR operations cause increased ATI and WATER, and assigns protection only to those vulnerable locations. This allows the system to use energy-assisted recording throughout the disk for high areal density while providing targeted mitigation in regions where interference is most severe.
4Reliability
If data refresh operations are performed frequently to mitigate ATI and WATER, then data integrity is improved, but I/O performance deteriorates
Solution Approach 1:
The patent applies preliminary action by proactively assigning guard band sectors to vulnerable regions before data corruption occurs. Instead of relying on frequent refresh operations to detect and correct errors, the system preemptively protects susceptible data by assigning guard band sectors in advance. This prevents ATI and WATER from corrupting data in the first place, eliminating the need for frequent refresh operations and their associated I/O performance penalties.
Solution Approach 2:
The patent converts the harmful effect of adjacent tracks into a beneficial protective mechanism. By assigning guard band sectors from adjacent tracks, the system uses the potentially harmful adjacent regions as a source of protection. The adjacent tracks, which could be sources of ATI and WATER, are instead utilized to provide guard band protection for vulnerable sectors, transforming a harmful factor into a beneficial defensive resource.
Data Source
AI summary
A Data Storage Device (DSD) includes a disk for storing user data in tracks including sectors. Adjacent Track Interference (ATI) values are determined for annular locations along a guard band location designated to not store user data and to separate a first region of tracks from a second region of tracks. Based on the ATI values determined for the annular locations, guard band sectors are assigned from one or more adjacent tracks of the second region corresponding to one or more locations where the one or more adjacent tracks are deemed more susceptible to data corruption based on the determined ATI values. The assigned guard band sectors form part of the guard band. According to one aspect, the ATI values are determined based on at least one Magnetic Recording Metric (MRM) and a track pitch.