Multi-Level Map Cache for NAND Flash Error Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
NAND flash memory systems face challenges with increasing bit error rates due to cell-to-cell interference and retention noise, leading to reduced storage capacity and device failure over operational cycles, as well as inefficiencies in garbage collection processes that can degrade performance and shorten device lifespan.
Innovation Solution
A media controller employing a multi-level map structure with a cache system that processes logical addresses to physical addresses, utilizing a Mega-TRIM operation to efficiently manage and update Block Used Space counts in the background, thereby reducing write amplification and extending device lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multi-level cell (MLC) flash memory is used to increase storage capacity, then more bits can be stored per cell, but cell-to-cell interference and retention noise increase leading to higher bit error rates
Solution Approach 1:
The patent introduces an intermediary error correction code (ECC) mechanism that acts as a mediator between the storage capacity and reliability contradiction. The ECC system detects and corrects errors caused by cell-to-cell interference and retention noise in MLC flash memory, allowing the system to maintain high storage capacity while compensating for the increased bit error rates through active error management rather than passive tolerance
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting operational parameters such as read threshold voltages and write pulse widths based on detected error patterns and retention characteristics. By modifying these parameters in response to changing memory conditions, the system optimizes the balance between storage density and error rates across different operational phases and degradation states
2Quantity of substance
If garbage collection is performed frequently to manage worn blocks, then storage capacity is maintained, but device lifespan is reduced due to increased erase cycles
Solution Approach 1:
The patent implements preliminary action through proactive wear leveling algorithms that predict and prevent block exhaustion before it occurs. The system continuously monitors block usage patterns and initiates preventive maintenance operations to distribute erase cycles evenly across all blocks, avoiding concentrated wear on specific blocks and extending overall device lifespan while maintaining storage capacity
Solution Approach 2:
The patent applies self-service through autonomous garbage collection and wear leveling mechanisms that automatically manage memory maintenance without external intervention. The system self-monitors block usage, self-schedules erase operations, and self-adjusts mapping tables to optimize wear distribution, reducing the need for external management while extending device operational life
3Device complexity
If traditional garbage collection is used, then data management is simple, but write amplification increases reducing system performance
Solution Approach 1:
The patent applies segmentation by dividing the garbage collection process into multiple independent phases: identification of valid/invalid blocks, scheduling of erase operations, relocation of valid data, and update of mapping tables. Each phase operates independently and can be optimized separately, reducing overall write amplification while maintaining manageable complexity through modular processing stages
Data Source
AI summary
Described embodiments provide a media controller that processes requests including a logical address and address range. A map of the media controller determines physical addresses of a media associated with the logical address and address range of the request. The map is a multi-level map having a plurality of leaf-level map pages that are stored in the media, with a subset of the leaf-level map pages stored in a map cache. Based on the logical address and address range, it is determined whether a corresponding leaf-level map page is stored in the map cache. If the leaf-level map page is stored in the map cache, a cache index and control indicators of the map cache entry are returned in order to enforce ordering rules that selectively enable access to a corresponding leaf-level map page based on the control indicators and a determined request type.