SSD Read Retry Bias Adaptation Without Test Reads
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Solution Overview
Problem
Existing SSD technologies face challenges in meeting quality of service (QoS) requirements due to reactive read retry mechanisms that fail to adapt read biases proactively, leading to potential violations of latency and reliability standards, especially in high-performance SSDs like PCIe Gen 6 enterprise SSDs.
Innovation Solution
A proactive history read adaptation method that optimizes read retry biases using recorded history entries without test reads, adapting read biases based on failed bit counts and retention time, ensuring efficient and reliable data retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reactive read retry mechanisms are used, then device complexity is reduced, but quality of service requirements cannot be met due to failure to adapt read biases proactively
Solution Approach 1:
The patent performs preliminary actions by proactively adjusting read biases before actual read operations based on recorded history entries. The controller predicts optimal read biases by analyzing past read operations and retention time patterns, rather than waiting for read failures to occur. This preliminary adaptation ensures QoS compliance by preventing read errors before they happen, especially for data that will be read after retention periods.
Solution Approach 2:
The patent implements feedback mechanisms by recording history entries of previous read operations and their outcomes. The controller continuously monitors read performance and uses this feedback to refine and update read bias values. This closed-loop feedback system allows the controller to learn from past operations and progressively improve read accuracy, ensuring sustained QoS compliance without increasing overall system complexity.
2Measurement precision
If test reads are performed to determine read retry biases, then read accuracy improves, but additional latency is introduced
Solution Approach 1:
The patent uses copying by maintaining recorded history entries that represent past read operation characteristics. Instead of performing actual test reads to determine optimal biases, the controller copies and analyzes historical data patterns to predict the best read bias values. This virtual copying approach provides accurate bias determination without the time penalty of physical test reads, thus improving read accuracy while minimizing latency.
Solution Approach 2:
The controller performs preliminary analysis of history entries and retention time to determine read retry biases before actual read operations. By calculating optimal biases in advance based on recorded data rather than through iterative test reads during the read path, the system achieves high measurement precision without introducing additional latency to the critical read operation timeline.
3Reliability
If read retry biases are not adapted proactively, then device complexity is low, but latency and reliability standards are violated
Solution Approach 1:
The patent implements self-service by enabling the controller to automatically adapt read biases using internally recorded history entries without requiring external intervention or complex external systems. The controller serves itself by monitoring its own read performance, storing history entries, and autonomously adjusting read bias values based on retention time and historical patterns. This self-service capability improves reliability while keeping the adaptation mechanism contained within the existing controller architecture.
Solution Approach 2:
The controller performs preliminary adaptation of read biases by analyzing history entries and retention time before executing read operations. This proactive bias adjustment ensures reliability standards are met by preventing read errors in advance, particularly for data accessed after storage retention periods. The preliminary action is implemented within the existing controller logic, avoiding the need for complex external adaptation systems.
Data Source
AI summary
A method and associated memory system for reading data from memory. The method and memory system perform read operations on the memory while recording as read retry (RR) biases a set of history entries of voltages used to read the memory; select from the set of history entries the RR biases for subsequent read operation of the memory without performing a test operation with any of the RR biases before the subsequent read operations; in the subsequent read operations, read the memory with one or more of the RR biases from the history entries; when a failed bit count is higher than a threshold for the subsequent read operations, evict a worst entry from the history entries and introduce a new history entry into the set of history entries; and update the RR biases based on the new history entry.