Dynamic Mapping Table Segmentation for SSD Space Waste
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Solution Overview
Problem
Rewritable non-volatile memory systems face inefficiencies due to dynamic changes in the size of physical-logical mapping tables, leading to unnecessary waste of system resources and reduced operation efficiency.
Innovation Solution
The method involves storing mapping records for physical erasing units with varying sizes, utilizing a memory control circuit unit to manage mapping records across multiple physical erasing units, and dividing the physical-logical mapping table into table pages based on the data bit area, with the number of table pages recorded in the redundancy bit area to efficiently utilize physical programming units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire physical-logical mapping table is written into the fixed space preserved in the active physical erasing unit, then the mapping relation can be stored, but space waste occurs when data compression efficiency is not as expected
Solution Approach 1:
The physical-logical mapping table is divided into multiple parts: a first part is stored in the fixed space of the active physical erasing unit, while a second part is stored in the buffer memory. This segmentation allows the system to store only the necessary mapping relations in the limited fixed space, avoiding space waste while maintaining reliable access to mapping information.
Solution Approach 2:
The system dynamically determines the size of the first part of the mapping table based on the actual data compression results. When compression efficiency is high, more mapping entries can be stored in the fixed space; when compression efficiency is low, fewer entries are stored there, adapting to the actual space available and preventing waste.
2Productivity
If the physical-logical mapping table size dynamically changes according to data compression, then data can be stored efficiently, but space waste occurs in the active physical erasing unit
Solution Approach 1:
The mapping table is segmented into a first part stored in the active physical erasing unit's fixed space and a second part stored in buffer memory. This allows the system to maintain dynamic adaptability to compression results while preventing space waste by only committing essential entries to the fixed space.
Solution Approach 2:
The buffer memory acts as an intermediary between the dynamic mapping table generation and the fixed space storage. It temporarily holds the mapping table, allowing the system to evaluate actual compression results and determine the optimal size of the first part to store in the fixed space, thus preventing space waste.
3Loss of substance
If the mapping table is stored in the buffer memory and fixed space, then space waste is prevented, but the system complexity increases
Solution Approach 1:
The system performs preliminary actions by first storing the mapping table in the buffer memory, then determining the appropriate size of the first part based on compression results before writing to the fixed space. This preliminary evaluation simplifies the overall process by avoiding repeated writes and complex real-time adjustments.
Solution Approach 2:
The system uses its own buffer memory resources to store the second part of the mapping table, eliminating the need for additional external storage resources. The buffer memory serves dual purposes: temporary data storage and mapping table storage, reducing overall system complexity despite the dual-location storage approach.
Data Source
AI summary
A mapping table accessing method for a rewritable non-volatile memory module is provided. The method includes: storing a mapping record corresponding to a first physical erasing unit into the first physical erasing unit, wherein the mapping record of the first physical erasing unit is a mapping relation of physical programming units in the first physical erasing unit. The method further includes: storing a mapping record corresponding to a second physical erasing unit into the second physical erasing unit, wherein the mapping record of the second physical erasing unit is a mapping relation of physical programming units in the second physical erasing unit. A size of the mapping record of the first physical erasing unit is different from a size of the mapping record of the second physical erasing unit.