Storage Controller RBER Self-Testing for Data Retention
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Solution Overview
Problem
Current methods for testing the reliability and data integrity of NAND flash memory devices are expensive and time-consuming, requiring extensive testing to determine end-of-life and data retention under various conditions, which can take years and vary across devices due to different cycling conditions.
Innovation Solution
A storage device with a controller that performs self-testing by measuring the raw bit error rate (RBER) of superblocks, estimating data retention time, and determining when to perform garbage collection, allowing for internal data validation and reduced testing needs for manufacturers and users.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manufacturers perform extensive reliability testing to accurately determine end-of-life and data retention, then measurement precision and reliability are improved, but testing time and cost increase significantly
Solution Approach 1:
The storage device performs self-testing of data retention by the controller reading back data from memory blocks and measuring raw bit error rates. This self-service approach eliminates the need for external manufacturer testing, allowing the device to monitor its own health and provide accurate retention data without requiring extensive external testing time and resources.
Solution Approach 2:
The system performs preliminary RBER measurements on memory blocks during normal operation or at scheduled intervals before actual failure occurs. By continuously monitoring and measuring retention characteristics in advance, the system can predict end-of-life conditions without requiring lengthy destructive testing to determine retention parameters.
2Reliability
If manufacturers perform extensive reliability testing to establish accurate data retention data points, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The storage device performs self-testing of data retention by the controller reading back data from memory blocks and measuring raw bit error rates. This self-service approach eliminates the need for external manufacturer testing, allowing the device to monitor its own health and provide accurate retention data without requiring extensive external testing time and resources.
Solution Approach 2:
The controller continuously monitors raw bit error rates from memory blocks and uses this feedback to estimate data retention time and determine when garbage collection should be performed. This feedback mechanism enables the system to maintain reliability through adaptive management without requiring expensive batch testing to establish retention characteristics.
3Measurement precision
If storage devices undergo extensive cycling condition testing to determine EOL, then measurement precision is improved, but device complexity and testing resources increase
Solution Approach 1:
The storage device performs self-testing of data retention by the controller reading back data from memory blocks and measuring raw bit error rates. This self-service approach eliminates the need for external manufacturer testing, allowing the device to monitor its own health and provide accurate retention data without requiring extensive external testing time and resources.
Solution Approach 2:
The system segments the storage device into manageable units (superblocks, blocks, pages) and performs targeted RBER measurements on specific segments during garbage collection operations. This segmentation allows precise measurement of retention characteristics in manageable portions without requiring complex system-wide testing procedures.
Data Source
AI summary
Aspects of a storage device including a memory and a controller are provided. The controller may determine to perform garbage collection on a superblock. During the garbage collection process, the controller will typically move the superblock into an erase pool for erasing the superblock. However, aspects of the disclosure are directed to a method of measuring a raw bit error rate (RBER) of the superblock prior to erasure. The measured RBER may be used to estimate a data retention time of the storage device and provide the customer with an early warning notification if a health metric of the storage devices reaches a threshold retention time.