Flash Storage CGI-WL Defect Isolation for Block Recovery
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Solution Overview
Problem
Flash storage devices face significant performance degradation when a common global interconnect-word line (CGI-WL) defect causes repeated program failures, leading to a rapid increase in marked bad blocks, which can trigger a read-only mode due to the depletion of available blocks.
Innovation Solution
A controller in the storage device identifies CGI-WL defects by analyzing logical address patterns and isolates the defective word lines, preventing further programming failures by maintaining a mapping of blocks to CGI sets and using isolation tables or hardware registers to exclude the defective word lines from programming operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the flash storage device marks blocks as bad blocks when program failures occur, then the reliability of data storage is improved, but the number of available blocks decreases, leading to read-only mode
Solution Approach 1:
The patent segments the problem by dividing blocks into different categories based on failure patterns. It identifies and isolates blocks with CGI-WL defects separately from other bad blocks, allowing non-defective blocks to remain available for use while only restricting access to genuinely defective blocks, thus preserving more available blocks while maintaining reliability
Solution Approach 2:
The patent changes the parameter of block status classification by introducing a specific defect type identification mechanism. Instead of uniformly marking all failed blocks as bad, it uses logical address pattern analysis to distinguish CGI-WL defective blocks, changing the state from 'all or nothing' to 'selective isolation', thereby maintaining more usable blocks
2Manufacturing precision
If the flash storage device performs comprehensive program operations on all word lines, then the data programming completeness is improved, but the occurrence of program failures increases when CGI-WL defects are present
Solution Approach 1:
The patent applies preliminary action by performing logical address pattern analysis before executing program operations. It identifies blocks with CGI-WL defects in advance using address pattern matching, then pre-excludes these blocks from programming operations, preventing program failures before they occur while ensuring safe blocks are properly programmed
Solution Approach 2:
The patent converts the harmful effect of CGI-WL defects into a beneficial filtering mechanism. By analyzing logical address patterns of failed blocks, it identifies and isolates defective blocks, transforming the problem of program failures into a solution that protects the overall system by preventing further failures in affected blocks
3Reliability
If the flash storage device enters read-only mode to prevent further block degradation, then the remaining blocks are protected from additional failures, but the device performance significantly decreases
Solution Approach 1:
The patent applies local quality by implementing selective isolation rather than global read-only mode. It identifies specific blocks with CGI-WL defects and isolates only those blocks from programming operations, while leaving all other blocks fully accessible and functional, thus maintaining high device performance while protecting against localized failures
Data Source
AI summary
Aspects of a storage device are provided for handling GBBs with defects between global interconnects and local word lines. The storage device includes a plurality of blocks each including a plurality of word lines, a plurality of interconnects within an interconnect set and between multiple ones of the blocks, volatile memory, and a controller. The controller determines a logical address pattern associated with the multiple ones of the blocks respectively including a program failure, determines whether the logical address pattern is associated with the interconnect set for the multiple ones of the blocks, determines a common word line associated with the program failures in the multiple ones of the blocks, un-marks these blocks as GBBs, and refrains from programming the common word line during respective program operations in the multiple ones of the blocks. Thus, blocks may be reclaimed, defective word line(s) isolated, and likelihood of read-only modes reduced.