Layered Decoder Reordering for Hard Disk Sector Reprocessing
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Solution Overview
Problem
Existing data processing systems, such as storage systems, face challenges in efficiently recovering data from sectors due to slower convergence rates in layered decoders and limited error correction capabilities, particularly in handling trapped sets and managing message updates across circulant layers.
Innovation Solution
The system employs a layered decoder with dynamic message update ordering, utilizing randomized reordering, error event-based reordering, and symbol log likelihood ratio (LLR) quality-based reordering to optimize message updates across circulant layers, enhancing error correction and data recovery from storage sectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a layered decoder is used to provide more effective trapping set handling, then error correction capability is improved, but convergence speed deteriorates
Solution Approach 1:
The patent applies dynamics by making the message update order adjustable and reconfigurable. The system dynamically changes the processing sequence of circulant layers based on detected error patterns, transitioning from a fixed predetermined order to an adaptive order that optimizes convergence speed for different error conditions while maintaining the layered decoder's error correction capability.
Solution Approach 2:
The patent changes the parameter of message update ordering by introducing multiple possible orders (different permutations of circulant layer processing sequences). By selecting and switching between different update orders as a controllable parameter, the system can optimize convergence behavior for different error scenarios without altering the fundamental layered decoder structure, thus resolving the contradiction between error correction capability and convergence speed.
2Device complexity
If message updates follow a predetermined order in layered decoder, then device complexity is reduced, but adaptability to different error patterns deteriorates
Solution Approach 1:
The system introduces dynamic reconfigurability to the message update process. Instead of a single fixed order, the decoder can adaptively select from multiple predefined update orders based on the specific error patterns detected in the data being processed. This dynamic adaptation improves versatility without requiring complex real-time generation of update sequences.
Solution Approach 2:
The patent implements periodic switching between different message update orders. The system can cycle through different ordering strategies or switch between orders at regular intervals or based on error pattern detection cycles. This periodic variation in processing order allows the decoder to adapt to different error patterns while maintaining a manageable set of predefined orders, balancing adaptability with device complexity.
Data Source
AI summary
A system is described for recovering data from a number of sectors, such as the sectors of a hard disk drive (HDD) disk platter, and so forth. The system receives data from the sectors via a read channel and uses a layered data decoder to recover data from the sectors. A memory is coupled with the processor and configured to retain data received from one or more of the sectors, e.g., in retained sector reprocessing (RSR) embodiments. The system is configured to update messages in different circulant layers of the data decoder's parity-check matrix. The system uses one message update order in a processing iteration, and different message update orders in subsequent reprocessing iterations. In some embodiments, layer reordering is used for RSR. In some embodiments, circulant reordering is used for RSR.