Magnetic Disk RRO Correction Using Adjacent Servo Post Codes
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Solution Overview
Problem
In magnetic disk devices, frequent occurrence of read errors in servo sectors due to repeatable runout (RRO) correction issues leads to off-track events, resulting in degraded write performance and increased write retry frequencies.
Innovation Solution
The magnetic disk device employs a controller that changes the RRO correction value based on adjacent servo sectors' post codes, using interpolation values or alternative RRO correction values to maintain accurate positioning and reduce off-track occurrences, thereby tightening the write-offtrack slice (WOS) and improving write performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the magnetic head position is strictly monitored within the write permitted range, then data write accuracy is improved, but write performance degrades due to increased retry frequency
Solution Approach 1:
The patent changes the RRO correction value parameter dynamically based on read error occurrences. When read errors occur in servo sectors, the system adjusts the RRO correction value to compensate for positioning deviations, thereby maintaining accurate head positioning without requiring excessive write retries
Solution Approach 2:
The system implements feedback by monitoring read errors in servo sectors and using this information to adjust the RRO correction value. The post code indicating RRO correction amount is read from servo sectors, and when read errors occur, the system feeds back this error information to modify the correction value, creating a closed-loop control system that improves positioning accuracy
2Measurement precision
If the RRO correction value is adjusted frequently to maintain positioning accuracy, then head positioning precision is improved, but system complexity increases
Solution Approach 1:
The patent applies local quality by adjusting the RRO correction value specifically for affected servo sectors where read errors occur, rather than uniformly adjusting all sectors. This localized adjustment approach maintains positioning precision in problematic areas while keeping the overall control system relatively simple
Solution Approach 2:
The system implements dynamics by making the RRO correction value adjustable and changeable based on operational conditions. The correction value is not fixed but can be modified when read errors are detected, allowing the system to adapt to changing positioning conditions without requiring a completely complex control architecture
Data Source
AI summary
According to embodiments, a magnetic disk device includes a magnetic disk, a magnetic head, and a controller. In the magnetic disk, a plurality of servo sectors is arranged in a circumferential direction. Servo information including a post code indicating a repeatable runout (RRO) correction amount is written to each of the plurality of servo sectors. The magnetic head writes and reads data to and from the magnetic disk. In positioning control for the magnetic head, when a read error of a first post code continuously occurs, the controller uses a first RRO correction value, which is different from a second RRO correction value based on the RRO correction value indicated by the first post code. The first post code is a post code of a first servo sector, which is one of the plurality of servo sectors.