Check After Write Wear Degradation Assessment
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Solution Overview
Problem
Existing solid state systems face challenges in differentiating between various error types and sources in read-back data, leading to inadequate responses to specific error conditions, particularly distinguishing between wear-related degradation and other noise sources.
Innovation Solution
A Check After Write (CAW) process is implemented, which involves programming a group of solid state storage cells, waiting for a predetermined time, and then reading them using a default or optimal read threshold to assess wear-related degradation by comparing bit errors, thereby differentiating between noise sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional error detection methods are used in solid state systems, then errors in read-back data can be detected, but the different error types and error sources cannot be differentiated
Solution Approach 1:
The patent segments error analysis into distinct categories by implementing separate testing protocols: Check After Write (CAW) for wear-related errors and Background Media Scan (BMS) for retention errors. This segmentation allows the system to differentiate between error types and apply targeted responses to each category, resolving the contradiction between error differentiation capability and analysis complexity.
2Reliability
If comprehensive error checking is performed on all solid state storage cells, then all error types can be detected, but the system response time and resource consumption increase
Solution Approach 1:
The patent implements periodic error checking with different frequencies for different cell groups. High-priority cells undergo frequent CAW testing, while low-priority cells undergo less frequent BMS testing. This periodic action with varying intensities maintains comprehensive error detection capability while reducing overall system response time and resource consumption.
Solution Approach 2:
The patent applies partial checking strategies where not all cells are checked with the same thoroughness. Critical cells receive intensive CAW testing, while non-critical cells receive lighter BMS testing. This partial action approach maintains system reliability for critical operations while reducing total checking time and resource usage.
3Reliability
If Check After Write testing is performed on all solid state storage cells, then wear-related degradation can be identified, but the productivity of the storage system decreases
Solution Approach 1:
The patent applies local quality by performing CAW testing selectively on specific cell groups rather than uniformly across all cells. Cells are categorized into different priority levels, and CAW testing is concentrated on high-priority cells showing wear symptoms. This localized approach maintains accurate wear degradation detection where needed while preserving overall system productivity.
Solution Approach 2:
The patent performs preliminary error characterization through BMS testing before applying more intensive CAW testing. This preliminary action identifies cells that actually need detailed wear analysis, allowing the system to skip unnecessary CAW tests on healthy cells and thereby maintain productivity while ensuring reliable wear detection when required.
Data Source
AI summary
A group of one or more solid state storage cells is programmed. A predetermined amount of time after the group of solid state storage cells is programmed, the group of solid state storage cells is read to obtain read data. Error correction decoding is performed on the read data and the group of solid state storage cells is assessed for wear related degradation based at least in part on the error correction decoding.