Shingled Band Rewrite Thresholds for SMR Storage
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Solution Overview
Problem
Shingled magnetic recording (SMR) technologies face inefficiencies due to the need for rewriting entire bands when errors occur, leading to performance degradation and resource consumption, especially when dealing with adjacent track interference (ATI) and error scans, which can cause timeouts and data quality issues.
Innovation Solution
Implementing a system that increments rewrite counts for bands and regions, allowing for partial or full read-modify-write (RMW) operations based on thresholds, thereby bypassing error scans and reducing the need for rewriting entire bands, and using a controller to manage these operations efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error scans are performed on shingled tracks to detect and correct writing errors, then data quality is improved, but device timeouts increase and performance degrades
Solution Approach 1:
The system performs preliminary actions by proactively rewriting bands when the rewrite count exceeds thresholds, before errors can accumulate and require error scans. This preventive approach maintains data quality while avoiding the time-consuming error scan process that causes timeouts
Solution Approach 2:
The system implements feedback mechanisms by monitoring rewrite counts and using this information to trigger band rewrites when thresholds are exceeded. This feedback loop enables the system to maintain data quality through proactive management rather than reactive error scanning, thereby reducing timeouts
2Reliability
If entire bands are rewritten when errors occur in shingled magnetic recording, then data quality is maintained, but resource consumption increases and performance degrades
Solution Approach 1:
The system divides the storage medium into bands and tracks, allowing selective rewriting of only the necessary portions rather than entire bands. This segmentation enables efficient resource usage by rewriting only the specific tracks or regions that require correction, maintaining data quality while reducing overall resource consumption
Solution Approach 2:
The system applies local quality by rewriting only the specific regions that need correction based on error detection and rewrite count thresholds, rather than uniformly rewriting entire bands. This localized approach maintains data quality in affected areas while minimizing resource consumption in unaffected areas
3Reliability
If rewrite operations are performed frequently to correct adjacent track interference, then data quality is improved, but productivity decreases due to increased operation time
Solution Approach 1:
The system performs preliminary rewrite operations when rewrite counts reach thresholds, addressing potential data quality issues before they require more frequent corrections. This proactive approach reduces the overall frequency of rewrite operations, thereby improving productivity while maintaining data quality
Solution Approach 2:
The system implements periodic rewrite operations based on monitored rewrite counts and thresholds, rather than continuous or frequent rewriting. This periodic approach maintains data quality through scheduled corrections while maximizing productivity by minimizing the frequency and duration of rewrite operations
Data Source
AI summary
Systems and methods are disclosed for performing band rewrites on shingled storage media based on error scan counts. In one embodiment, a device may comprise a data storage medium including a first band and a processor. The first band may include a plurality of tracks storing data in a shingled manner where a first track at least partially overlaps a second track. The processor may be configured to receive a write command directed to the first band, increment a first rewrite count of the first band based on the write command, and when the first rewrite count exceeds a first rewrite threshold, perform a read-modify-write (RMW) operation for all of the first band. In some embodiments, a device may maintain write counts for sections of a band, and perform RMW operations on less than all of the band.