Memory System Write Suppression for NAND Lifespan
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Solution Overview
Problem
NAND flash memory in SSDs has a limited number of write cycles, leading to a shortened lifespan due to unrestricted writing from buffer memory, which is not effectively managed by existing technologies.
Innovation Solution
A memory system with a write suppression management unit that temporarily writes data to a buffer memory and only writes it to NAND flash memory upon a flush request or power shutdown, utilizing a DRAM with a power storage device to manage data transfer and prevent unnecessary writing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If data is continuously written to NAND flash memory from buffer memory, then write performance is maintained, but the lifespan of NAND flash memory is shortened due to excessive write cycles
Solution Approach 1:
The patent introduces a write suppression management unit as an intermediary between the buffer memory and NAND flash memory. This unit selectively suppresses write operations to the NAND flash memory based on management information, allowing data to remain in the buffer memory longer and reducing write cycles to the NAND flash memory, thereby extending its lifespan while maintaining performance through controlled data transfers.
Solution Approach 2:
The patent implements preliminary action by pre-managing write suppression before data is actually written to the NAND flash memory. The write suppression management unit proactively controls which data should be written to the buffer memory and which should be directly flushed to the NAND flash memory, preventing unnecessary write cycles and extending the lifespan of the NAND flash memory.
2Reliability
If write suppression management is implemented to extend NAND flash memory lifespan, then write cycles are reduced, but device complexity increases due to additional management units and control mechanisms
Solution Approach 1:
The write suppression management unit is designed with multi-functionality, serving multiple purposes: it manages write suppression to extend NAND flash memory lifespan, controls data caching in the buffer memory, and coordinates with the host system through flush requests. By consolidating these functions into a single unit, the patent reduces overall system complexity compared to having separate management mechanisms for each function.
3Reliability
If data is held in buffer memory without flushing, then write operations are suppressed and NAND flash memory lifespan is extended, but data loss risk increases during unexpected power shutdown
Solution Approach 1:
The patent implements feedback mechanisms where the write suppression management unit continuously monitors system state and responds to flush requests from the host system. When a flush request is received or abnormal termination is detected, the unit immediately transfers data from the buffer memory to the NAND flash memory, ensuring data safety while maintaining write suppression during normal operation.
Solution Approach 2:
The patent prepares for data loss by maintaining a buffer memory that can hold data temporarily, and by implementing automatic flush mechanisms that activate under specific conditions (flush requests, abnormal termination). This cushioning approach allows the system to extend NAND flash memory lifespan through write suppression while having pre-prepared mechanisms to prevent actual data loss.
4Quantity of substance
If DRAM storage capacity is increased to match NAND flash memory capacity, then data retention is improved, but manufacturing cost increases
Solution Approach 1:
Instead of providing full DRAM capacity equal to NAND flash memory capacity, the patent implements partial action by using write suppression management to control data transfers selectively. The buffer memory only needs to accommodate actively being written data rather than the entire storage capacity, significantly reducing the required DRAM capacity and manufacturing cost while still providing effective data retention during write operations.
Data Source
AI summary
A memory system includes a non-volatile memory, a buffer memory, and a controller. The controller is configured to write data corresponding to a write command received from a host in the buffer memory, and based on an indication from the host, do not write the data stored in the buffer memory into the non-volatile memory unless a non-volatilization event occurs, the non-volatilization event being one of a flush request from the host and a detection of a power shutdown.