Nonvolatile Memory Read Recovery Under Host Time Limits
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Solution Overview
Problem
Semiconductor memory systems face challenges in recovering data within specified time limits due to high error rates, especially when multiple or lengthy data recovery operations exceed these limits, leading to undesirable failures in responding to host read commands.
Innovation Solution
Implement a memory system that performs a first data recovery operation within the time limit, informs the host of its failure, and allows for subsequent read commands to enable additional recovery operations, including pausing and unpausing these operations as needed to extend the recovery time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple data recovery operations are performed to recover data with high error rates, then data recovery reliability is improved, but the operation time exceeds the specified time limit
Solution Approach 1:
The patent segments the data recovery process into multiple independent recovery operations that can be executed sequentially. Each recovery operation attempts to correct errors using different methods, and if one fails, the next operation is initiated. This segmentation allows the system to maintain high recovery reliability while managing time consumption by breaking down the complex recovery task into manageable stages.
Solution Approach 2:
The patent implements preliminary actions by performing quick recovery operations first before proceeding to more time-consuming recovery methods. The system attempts fast error correction techniques initially, and only if those fail does it proceed to slower, more thorough recovery operations. This preliminary action approach ensures that most recoveries are completed within the time limit while still maintaining the capability to handle difficult cases.
2Productivity
If a single fast data recovery operation is performed to meet the time limit, then operation speed is improved, but data recovery reliability deteriorates
Solution Approach 1:
The patent employs dynamic adjustment of recovery strategies based on the characteristics of the data and the time remaining. The system can switch between fast and slow recovery operations dynamically, selecting the appropriate recovery method based on real-time conditions. This dynamic approach allows the system to optimize between speed and reliability depending on the specific situation.
Solution Approach 2:
The patent changes operational parameters such as the complexity and duration of recovery operations based on the data error rate and time constraints. When data shows high error rates, the system adjusts by allocating more time to recovery operations or switching to more sophisticated recovery algorithms. This parameter adjustment enables the system to adapt its speed-reliability tradeoff to match the actual conditions.
3Reliability
If multiple data recovery operations are implemented to ensure data recovery, then data recovery capability is improved, but the system complexity increases
Solution Approach 1:
The patent implements a universal recovery framework that can handle multiple types of errors and data conditions using a standardized multi-operation approach. The same set of recovery operations is used regardless of the specific error type or data characteristics, simplifying the control logic while maintaining high recovery capability. This universal approach reduces system complexity by avoiding the need for specialized recovery routines for different scenarios.
Data Source
AI summary
A data storage system includes control circuits configured to connect to nonvolatile memory cells and to a host. The control circuits are configured to perform a first data recovery operation in response to reading uncorrectable data from the nonvolatile memory cells. The control circuits are configured to inform the host, within a time limit for responding to a host read command from the host, of the failure of the first data recovery operation and availability of a second data recovery operation.