Flash Memory Controller Trim Command SPOR Data Integrity
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Solution Overview
Problem
In flash memory devices, sudden power off recovery (SPOR) after a trim command can lead to errors during the rebuilding of mapping tables, resulting in data recovery issues when the logical address region corresponds to an active block.
Innovation Solution
A method involving the use of a physical address to logical address mapping table (F2H mapping table) and a flush-bitmap to ensure correct mapping table reestablishment, where flush bits indicate updated physical addresses, and the updated tables are written into the flash memory module upon receiving a trim command.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the flash memory device updates only the logical address to physical address mapping table (H2F mapping table) when receiving a trim command, then the operation speed is fast, but data recovery may occur during sudden power off recovery (SPOR) resulting in loss of data integrity
Solution Approach 1:
The patent applies preliminary action by updating the flush-bitmap before executing the trim command. The flush-bitmap records which physical addresses have been updated in the H2F mapping table. During SPOR recovery, this pre-updated flush-bitmap allows the system to correctly identify which mappings are valid, preventing data recovery issues while maintaining fast trim command execution.
Solution Approach 2:
The patent introduces the flush-bitmap as an intermediary data structure between the H2F mapping table and the F2H mapping table. This intermediary records the update status of physical addresses, enabling the system to reconcile mapping information during SPOR without requiring complete rewriting of mapping tables, thus balancing speed and reliability.
2Reliability
If the flash memory device maintains both F2H mapping table and H2F mapping table with flush-bitmap updates, then data integrity during SPOR is ensured, but the device complexity increases
Solution Approach 1:
The patent segments the mapping table management into two distinct structures: the H2F mapping table (logical to physical addresses) and the F2H mapping table (physical to logical addresses), with the flush-bitmap tracking updates. This segmentation allows each structure to be updated independently and efficiently, reducing the complexity of managing a single comprehensive mapping table while ensuring data integrity during SPOR.
3Measurement precision
If the flush-bitmap is updated for every physical address in the F2H mapping table, then accurate tracking of updated mappings is achieved, but the time required for mapping table updates increases
Solution Approach 1:
The patent applies partial action by updating only the necessary portions of the flush-bitmap corresponding to physical addresses that are actually modified during trim operations. Instead of updating the entire flush-bitmap for every operation, the system selectively updates only the relevant entries, maintaining precise tracking of mapping updates while minimizing the time overhead.
Data Source
AI summary
The present invention provides a method for accessing a flash memory module, wherein the method includes the steps of: writing data into a plurality of pages of a specific block, and establishes or updates a F2H mapping table based on physical addresses of the plurality of pages and logical addresses of the data; using the F2H mapping table to update a H2F mapping table; initializing a flush-bitmap, wherein the flush-bitmap records a plurality of flush bits corresponding to the physical addresses of the plurality of pages, respectively; receiving a trim command from a host device, wherein the trim command asks to mark at least one of the logical addresses of the data as invalid; updating the H2F mapping data according to the trim command; updating the flush-bitmap according to the trim command; and writing the updated H2F mapping table and the updated flush-bitmap into the flash memory module.