Flash Data Retention Control Using Dynamic ECC and Scrubbing
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Solution Overview
Problem
Flash memory systems in embarked environments face challenges in retaining data due to increased bit errors from high temperatures and extended power outages, requiring dynamic adjustment of data protection schemes to balance error correction and performance.
Innovation Solution
A computer-implemented method and system that dynamically adjusts the data scrub frequency and error correcting code (ECC) scheme based on characterization data and measured parameters, such as temperature and program/erase cycles, to optimize data protection upon power restoration, using look-up tables to determine the appropriate data protection scheme.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a robust ECC scheme is applied to protect against bit errors in high temperature environments, then data reliability is improved, but system performance deteriorates
Solution Approach 1:
The patent dynamically adjusts the ECC scheme and data scrub frequency based on real-time temperature readings and power-off duration. Instead of using a fixed robust ECC scheme that always degrades performance, the system adapts the level of protection to current environmental conditions, using stronger ECC only when temperature and power-off duration indicate high risk of bit errors.
Solution Approach 2:
The system changes operational parameters (ECC strength and scrub frequency) based on measured environmental parameters (temperature and power-off duration). By monitoring these parameters and adjusting protection levels accordingly, the system optimizes the balance between reliability and performance for each specific operating condition.
2Reliability
If frequent data scrubs are performed to detect bit errors, then data reliability is improved, but system performance deteriorates
Solution Approach 1:
The patent implements dynamic adjustment of data scrub frequency based on temperature and power-off duration. When the system detects high temperature conditions or extended power-off periods, it increases scrub frequency to detect potential bit errors. Conversely, under normal conditions, scrub frequency is reduced to minimize performance impact.
Solution Approach 2:
The system modifies the operational parameter of scrub frequency according to environmental parameters. By changing scrub frequency dynamically rather than maintaining a fixed high frequency, the system achieves reliable error detection only when environmental conditions warrant such protection, thereby preserving performance during normal operation.
3Reliability
If strong ECC and frequent scrubs are applied to all data, then data protection is improved, but the complexity of the system increases
Solution Approach 1:
The patent introduces dynamic decision-making logic that adjusts protection levels based on environmental conditions. The system evaluates temperature and power-off duration to determine the appropriate ECC strength and scrub frequency, rather than applying maximum protection uniformly. This dynamic approach reduces unnecessary complexity in normal operating conditions while maintaining high protection when needed.
4Reliability
If maximum ECC protection is used during extended power-off periods, then data reliability is improved, but the loss of performance during operation increases
Solution Approach 1:
The patent performs preliminary assessment of environmental conditions (temperature and power-off duration) to predict the risk of bit errors before data access operations. Based on this preliminary assessment, the system proactively adjusts ECC strength and scrub frequency to match the actual risk level, avoiding unnecessary performance degradation when the risk is low while ensuring adequate protection when risk is high.
Data Source
AI summary
A data retention methodology for use in electrically rewritable nonvolatile storage systems is disclosed. The methodology collects characterization data of the storage system (e.g., time stamps, program/erase cycles, sensed temperature over time, and others) and uses at least a portion of that data to associate various data retention schemes with the collected characterization data. At power-on, the methodology determines a duration of a time during which power was not supplied to the storage system. The methodology also uses the power-on time to trigger the selection of an appropriate data protection scheme (e.g., enhanced ECC and/or read/scrub frequency). Dynamic selection and adjustment of the applied protection scheme may be based on the predetermined and/or calculated association between various protection schemes and the collected characterization data of the storage system.