Flash Memory Retention Manager for Offline Data Integrity
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Solution Overview
Problem
Non-volatile semiconductor memory devices, such as flash memory devices, face challenges in securing data integrity when disconnected from a host for an extended period, as they lack a mechanism to determine and perform retention operations independently.
Innovation Solution
A data retention method and system that involves sampling non-volatile memory devices to detect retention information, determining the need for a retention operation based on read voltage shift values and read errors, and performing the operation accordingly, ensuring data reliability even when disconnected from the host.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the flash memory device performs retention operation only when connected to a host, then the device can maintain data integrity during normal operation, but data cannot be secured when the device is in offline state for longer than the retention period
Solution Approach 1:
The flash memory device is equipped with a retention manager that enables it to autonomously perform retention operations without requiring host connection. The device independently monitors retention periods, detects when retention is needed, and executes retention operations on its own, transforming from a host-dependent system to a self-sufficient system that can maintain data integrity even when offline
Solution Approach 2:
The retention manager proactively monitors the retention period and performs retention operations before data degradation occurs. By continuously tracking the time since last retention and comparing it against the retention period threshold, the system takes preliminary action to prevent data loss before the offline state becomes problematic
2Reliability
If the flash memory device continuously performs retention operations, then data integrity is maintained, but power consumption increases and operation efficiency decreases
Solution Approach 1:
Instead of continuous retention operations, the system implements periodic retention based on the retention period parameter. The retention manager periodically evaluates whether the current time exceeds the retention period and only performs retention operations when necessary, converting continuous power-consuming operations into periodic, condition-based actions that maintain data integrity while minimizing energy consumption
Solution Approach 2:
The system dynamically adjusts retention operations based on the retention period parameter and current operational state. By monitoring the elapsed time against the retention period threshold, the system changes its behavior from inactive to active only when the parameter condition (time > retention period) is met, optimizing the balance between data retention and power consumption
3Reliability
If the flash memory device performs retention operation on all memory cells, then complete data protection is achieved, but operation time and power consumption increase significantly
Solution Approach 1:
The retention operation is selectively applied only to specific memory blocks that require retention rather than uniformly to all memory cells. The retention manager identifies and targets only those blocks where the retention period has been exceeded, applying retention operations locally to affected areas while leaving other blocks unchanged, thereby reducing overall operation time and power consumption while maintaining complete protection coverage for data that actually needs protection
Data Source
AI summary
A data retention method that includes sampling a plurality of nonvolatile memory devices included in a data storage device to detect retention information for each of the nonvolatile memory devices in response to a request of a host and outputting, from the data storage device to the host, sampling data based on a result of the sampling, determining, at the host, whether to perform a retention operation on each of the nonvolatile memory devices based on the sampling data, and performing the retention operation on each of the nonvolatile memory devices based on a result of the determination.