Flash Memory Data Erasure via Copy-Before-Erase
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Solution Overview
Problem
In flash memory modules, deleted data can still be recovered and stolen due to the lack of effective data erasure methods, as marking physical programming units as invalid does not guarantee actual data deletion.
Innovation Solution
A data erasing method that groups physical erasing units into data and spare areas, where valid data is copied and erased from the marked units in the data area, and mapped to spare units, ensuring physical erasure and preventing data recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If physical programming units are marked as invalid when data is deleted, then the logical structure is simplified and write operations can proceed, but the actual data remains in the memory and can be recovered
Solution Approach 1:
The patent applies preliminary action by performing data copying from invalid physical programming units to valid units before erasing the original data. The memory control circuit identifies invalid units, copies their data to valid units in the same erasing unit, and then erases the invalid units. This ensures data is securely removed before the operation completes, preventing any potential recovery while maintaining operational simplicity.
2Reliability
If data is physically erased from marked units, then data security is improved, but the complexity of the deletion process increases
Solution Approach 1:
The patent implements self-service by enabling the memory control circuit to automatically manage the entire data erasure process without external intervention. When a delete command is received, the controller autonomously identifies invalid physical programming units, copies their data to valid units within the same erasing unit, erases the invalid units, and updates the mapping table. This automation hides the complexity from users while ensuring secure data erasure.
3Reliability
If valid data is copied to spare area units before erasing data area units, then data recovery is prevented, but the time required for deletion increases
Solution Approach 1:
The patent applies segmentation by dividing the memory into distinct data area and spare area, and further segmenting erasing units into valid and invalid physical programming units. This segmentation allows selective copying of data from invalid units to valid units within the same erasing unit, enabling parallel processing and reducing overall deletion time while maintaining data security through the copy-before-erase mechanism.
Data Source
AI summary
A data erasing method for a rewritable non-volatile memory module is provided. The method includes receiving a predetermined command for performing on a first logical sub-unit from a host system; marking a first physical programming unit mapped to the first logical sub-unit as being in an invalid data status and recording a mark for a first physical erasing unit that the first physical programming unit belongs to, in response to the predetermined command. The method further includes selecting the first physical erasing unit according to the mark, copying valid data in the first physical erasing unit to a second physical erasing unit gotten from a spare area of the rewritable non-volatile memory module and erasing data stored in the first physical erasing unit.