Hard Disk Control Unit Servo Sector Substitution
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Solution Overview
Problem
Conventional disk devices face inefficiencies in writing operations due to defects on magnetic disks, particularly when the length of user sectors exceeds that of servo sectors, leading to prolonged alternative operation times and reduced writing capacity.
Innovation Solution
Implementing a control unit that detects defective user sectors and conducts alternative operations per servo sector, which includes both the servo area and subsequent data area, allowing for immediate substitution without retry operations, thereby maintaining writing efficiency even when user sector lengths are enlarged.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If alternative operation is conducted per user sector when user sector length is enlarged to 4KB, then writing capacity is improved, but alternative operation time is prolonged
Solution Approach 1:
The invention segments the alternative operation process by introducing a track-based retry mechanism. When a write fault occurs, the system first retries within the same user sector (intra-sector retry). Only after exhausting retry attempts does it proceed to substitute the entire servo sector containing the defective user sector. This segmentation reduces the scope of alternative operations compared to conventional per-user-sector substitution, thereby shortening alternative operation time while preserving writing capacity.
Solution Approach 2:
The invention performs preliminary actions by pre-identifying defective user sectors through read operations before write operations. The defect management table is updated in advance to mark defective sectors, allowing the system to proactively plan alternative operations rather than reacting to write failures. This preliminary detection and marking process enables more efficient resource allocation and reduces the time required when alternative operations become necessary.
2Reliability
If retry operation is conducted multiple times before recognizing disabled servo sector, then reliability is improved, but alternative operation time is prolonged
Solution Approach 1:
The invention implements a dynamic alternative operation strategy that adapts the scope of substitution based on the frequency and pattern of write faults. The system monitors write operation results and dynamically adjusts between intra-sector retry and inter-sector substitution approaches. This dynamic behavior allows the system to maintain high reliability through multiple retries when appropriate, while quickly switching to sector substitution when defects are confirmed, thereby optimizing the balance between reliability and operation time.
Solution Approach 2:
The invention applies local quality by differentiating the handling of different regions within a servo sector. When a write fault occurs, the system first attempts localized repair within the affected user sector through retry operations. Only when the defect is confirmed persistent does it expand the alternative operation to the entire servo sector level. This localized approach minimizes the impact area and reduces alternative operation time while maintaining reliability through progressive escalation.
Data Source
AI summary
A hard disk includes: a plurality of servo areas which are elongated radially from a center of the hard disk to an outward thereof over tracks thereof; and a plurality of data areas which are respectively provided between the plurality of servo areas; wherein alternative operation is conducted per servo sector containing one of the plurality of servo areas and a data area provided subsequent to the one of the plurality of servo areas and having a defect created therein when a user sector containing at least a portion of the data area and functioning as an access unit has the defect therein.