Read-After-Write Error Correction for High-Density Magnetic Storage
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Solution Overview
Problem
Increasing tracks per inch (TPI) in data storage devices without compromising data integrity and performance, as adjacent tracks are susceptible to partial overwrites during write operations, leading to potential data loss and errors.
Innovation Solution
Implementing a method that identifies potentially-overwritten sectors on a previously-written track, performs read-after-write operations to correct errors, and stores data in a solid-state memory, allowing for increased TPI while maintaining data integrity and performance by using an off-track limit and mirroring data in dynamic random access memory (DRAM).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If tracks per inch (TPI) is increased to improve areal density, then storage capacity is improved, but data integrity deteriorates due to partial overwrites on adjacent tracks
Solution Approach 1:
The system performs read-after-write (RAW) operations immediately after write operations to detect and correct potential overwrite errors before they affect data integrity. This preliminary detection and correction mechanism allows the system to maintain high TPI while preventing data loss from track encroachment
Solution Approach 2:
The system implements a feedback loop where write operations trigger subsequent read operations to verify data integrity. The controller monitors for encroachment conditions and initiates corrective actions based on the read results, creating a closed-loop system that maintains reliability at high densities
2Reliability
If read-after-write operations are performed to correct errors and maintain data integrity, then reliability is improved, but IOPS performance deteriorates
Solution Approach 1:
The system applies RAW operations selectively only to sectors that are likely to be affected by encroachment, rather than performing reads on entire tracks. This localized approach maintains data integrity for at-risk sectors while minimizing the performance impact on overall IOPS
Solution Approach 2:
The system performs read operations on a partial basis - only on sectors that are potentially affected by track encroachment rather than all sectors. This partial action approach provides sufficient error detection and correction while avoiding the full performance penalty of comprehensive reads
3Reliability
If data is stored in solid-state memory and mirrored in DRAM to manage write faults, then data integrity is improved, but device complexity increases
Solution Approach 1:
The system creates mirrored copies of data in DRAM from the solid-state memory. This copying mechanism provides redundant storage that can be used for rapid error detection and correction, maintaining data integrity while using well-understood memory technologies
Solution Approach 2:
The controller acts as an intermediary that manages the complexity of coordinating between solid-state memory and DRAM. It handles the mirroring operations, error detection, and correction logic, isolating the complexity from the rest of the system while maintaining simple interfaces
Data Source
AI summary
A method includes writing first data on a first track of a data storage surface, and storing information for the first data in a memory other than the data storage surface. The method also includes performing a write operation on a second track of the data storage surface after the data is written on the first track. The second track is adjacent to the first track. The method further includes identifying potentially-overwritten sectors of the first track as a result of the performance of the write operation on the second track, and performing a first read operation on the identified potentially-overwritten sectors of the first track after completion of the write operation on the second track. Second data associated with the identified potentially-overwritten sectors is then stored in a solid-state memory, and mirrored to media.