Memory Controller Data Integrity Tracking

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Solution Overview

Problem

The frequent access to nonvolatile memory systems, such as NAND flash memory, for processes like patrol and scrubbing leads to wear and tear, necessitating a method to maintain data integrity while reducing the number of read operations.

Innovation Solution

A memory system with a controller that manages storage areas by tracking the last confirmation time of data integrity using a verify status management table, allowing for controlled verify processes and reducing unnecessary reads by skipping operations on data confirmed within a certain time frame.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If frequent patrol and scrubbing processes are performed to maintain data integrity, then data reliability is improved, but memory wear increases

Engineering Contradiction:

Improvedata integrityVSAvoidmemory wear

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The controller performs verify processes in advance during write operations and updates the verify status management table accordingly. This preliminary action allows the system to skip future verify operations for data already confirmed as intact, thereby reducing unnecessary read accesses and memory wear while maintaining data reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The verify status management table automatically tracks the last verified time for each storage area, enabling the controller to make autonomous decisions about which areas require verification. This self-service mechanism eliminates the need for comprehensive periodic scrubbing of all data, reducing memory access frequency while ensuring data integrity

Inventive Principle:

Principle #25Self-service

2Reliability

If comprehensive verify processes are performed on all data, then data integrity is ensured, but access time increases

Engineering Contradiction:

Improvedata integrityVSAvoidaccess time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The storage space is divided into multiple storage areas, and the verify status management table maintains separate last verified time information for each area. This segmentation allows the controller to selectively verify only specific storage areas that require it, rather than performing comprehensive verify processes on all data, thereby reducing access time while ensuring data integrity where needed

Inventive Principle:

Principle #1Segmentation

3Reliability

If periodic scrubbing is performed on all data, then data integrity is maintained, but the frequency of read operations increases

Engineering Contradiction:

Improvedata integrityVSAvoidread operation frequency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

Instead of performing verify processes on all data during periodic scrubbing, the controller uses the verify status management table to identify and verify only storage areas whose last verified time exceeds a predetermined threshold. This partial action approach maintains data integrity for areas that need it while significantly reducing the frequency of read operations compared to comprehensive periodic scrubbing

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11816344B2Memory system in which information on a time in which integrity of a stored data piece is confirmed last

Publication Date: 2023.11.14 KIOXIA CORP

AI summary

According to one embodiment, a memory system includes a nonvolatile memory and a controller. The controller manages at least one storage area that is obtained by logically dividing a storage space of the nonvolatile memory. One or more storage areas in the at least one storage area store one or more data pieces, respectively. The controller manages first information on one or more times in which integrity of the one or more data pieces have been confirmed last, respectively.