Read Retry Method for Solid State Storage Devices
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Solution Overview
Problem
Conventional solid state storage devices experience increased latency and read failures due to the lengthy read retry process, which is triggered by distorted threshold voltage distribution curves caused by operating conditions such as read disturbing and data retention issues, leading to unsuccessful read actions and time-outs.
Innovation Solution
A read retry method that includes a failure mode judgement module to adjust the read retry process based on specific failure modes, such as program failure, write/read temperature difference, read disturbing, and data retention modes, by applying corresponding retry read voltage sets and processes to reduce the retry time and avoid time-outs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional read retry process is performed when threshold voltage distribution curves are distorted, then data reliability is maintained through multiple retry attempts, but read latency increases and time-outs occur
Solution Approach 1:
The patent applies preliminary action by performing read level calibration before the read retry process. The calibration process adjusts read levels based on threshold voltage distribution characteristics in advance, so when a read failure occurs, the retry can use pre-calibrated read levels rather than performing full calibration during retry, significantly reducing latency while maintaining data reliability
Solution Approach 2:
The patent segments the read retry process into different scenarios based on failure causes. By identifying specific failure modes (read disturbing, data retention, program failure), the system applies targeted retry strategies for each scenario rather than using a uniform retry process, reducing unnecessary retry attempts and associated latency
2Reliability
If multiple retry read voltage sets are applied to handle different failure modes, then read success rate improves, but the complexity of the read retry process increases
Solution Approach 1:
The patent implements dynamic adjustment of read levels during the read retry process. The read level calibration module dynamically calculates optimal read levels based on actual threshold voltage distribution feedback from failed read attempts, allowing the system to adapt to different failure modes without requiring static pre-programmed voltage sets for every possible scenario, thus managing complexity while maintaining high success rates
3Measurement precision
If read level calibration is performed during read retry, then accurate data reading is achieved, but the time required for retry process increases
Solution Approach 1:
The patent performs read level calibration in advance before read operations, storing calibrated read levels in the system. When read failures occur, the pre-calibrated levels are applied immediately without performing full calibration during retry, maintaining read accuracy while minimizing the time penalty of calibration operations
Data Source
AI summary
A read retry method for a solid state storage device is provided. The solid state storage device is in communication with a host. The solid state storage device includes a non-volatile memory. The read retry method includes the following steps. Firstly, the solid state storage device judges whether a specified read block of the non-volatile memory is in a specified failure mode. If the specified read block of the non-volatile memory is in the specified failure mode, a failure mode read retry process corresponding to the specified failure mode is performed. If an accurate read data is acquired in the failure mode read retry process, the accurate read data is transmitted to the host. If the accurate read data is not acquired in the failure mode read retry process, a read fail message is sent to the host.