Magnetic Disk Controller Off-Track Sector Retry
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Solution Overview
Problem
Magnetic disk devices face inefficiencies in reading data due to off-track states, where the magnetic head deviates from the target track, leading to incorrect data reading and increased time and resource consumption for error correction.
Innovation Solution
A magnetic disk device with a controller that performs initial read operations, detects off-track states, and selectively retries reading specific sectors during subsequent revolutions, reducing the need for extensive error correction across all sectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the magnetic head reads all sectors on a track during each revolution, then complete data acquisition is achieved, but time and computational resources are wasted on sectors that can be correctly read without retry
Solution Approach 1:
The patent segments the track into individual sectors and tracks off-track states per sector. The controller identifies which specific sectors were read during off-track conditions and selectively retries only those sectors, rather than re-reading the entire track. This segmentation approach reduces unnecessary error correction operations on sectors that were successfully read.
2Reliability
If error correction is performed on all sectors during each read operation, then data reliability is maintained, but computational resources and time are consumed unnecessarily on sectors read during on-track states
Solution Approach 1:
The patent applies local quality by treating each sector differently based on its reading conditions. Sectors read during on-track states are processed normally, while only sectors identified as being read during off-track states undergo selective retry and enhanced error correction. This localized approach optimizes computational resources by applying intensive error correction only where needed.
3Reliability
If the magnetic head retries reading all sectors after detecting off-track state, then complete data recovery is achieved, but the time required for data acquisition increases significantly
Solution Approach 1:
The patent applies partial action by retrying reading operations only on the subset of sectors that were identified as being read during off-track states, rather than retrying all sectors on the track. This partial retry approach recovers data from off-track conditions while avoiding the excessive time consumption that would result from retrying the entire track.
Data Source
AI summary
A magnetic disk device includes a magnetic disk including a track having a plurality of sectors, a motor configured to rotate the magnetic disk, a magnetic head, and a controller. The controller is configured to perform a first read operation of reading target sectors among the sectors of the track, with the magnetic head during a first revolution of the magnetic disk, detect an off-track state of the magnetic head during the first revolution of the magnetic disk, perform a first error correction with respect to data read from the target sectors during the first read operation, and perform a second read operation of selectively reading a part of the target sectors for which the off-track state has been detected or the first error correction is unsuccessful, with the magnetic head during a second revolution of the magnetic disk.