Erase-Unit Buffering in Nonvolatile Storage to Reduce Write Amplification
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Solution Overview
Problem
The lifetime and reliability of nonvolatile memory devices, such as flash memory, are reduced due to repetitive write operations, which cause erase operations and increase write amplification factor (WAF), leading to decreased performance and durability.
Innovation Solution
A storage device with a reduced WAF is designed by employing a memory controller that assigns specific memory cells as y-level and x-level cells within erase units, allowing for sequential writes and data buffering, thereby minimizing unnecessary write operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If write operations are performed in nonvolatile memory, then data storage function is achieved, but lifetime and reliability are reduced
Solution Approach 1:
The patent introduces a buffer memory as an intermediary component between the host device and the nonvolatile memory. This buffer temporarily stores data before it is written to the nonvolatile memory, allowing the system to batch and optimize write operations. By using this intermediary, the frequency of write operations to the nonvolatile memory is reduced, thereby improving lifetime and reliability while maintaining data storage functionality.
Solution Approach 2:
The patent performs preliminary actions by pre-processing and buffering data before it is written to the nonvolatile memory. The buffer memory holds data in advance, allowing the system to consolidate write operations and reduce the total number of write cycles to the nonvolatile memory. This preliminary buffering action helps minimize wear on the memory cells while ensuring data is ready for efficient writing when needed.
2Productivity
If erase operations are performed between write operations, then write-before-erase characteristic is satisfied, but write amplification factor increases
Solution Approach 1:
The patent merges multiple write operations into single batched write operations by using the buffer memory to accumulate data. Instead of performing separate write operations that would each require erase operations, the system combines data from multiple sources and performs consolidated writes. This merging approach reduces the total number of erase operations needed, thereby lowering the write amplification factor while managing erase operations more efficiently.
3Speed
If sequential writes are permitted, then write speed is improved, but unnecessary write operations increase
Solution Approach 1:
The patent implements feedback mechanisms where the buffer memory and memory controller monitor the state of data and write operations. By tracking which data has been written and which is still pending, the system can identify and eliminate unnecessary write operations. The feedback loop allows the controller to optimize the sequence of writes, ensuring that data is written only when necessary and in the most efficient manner, thus maintaining high write speed while avoiding redundant operations that would harm reliability.
Data Source
AI summary
In some embodiments, a storage device includes a nonvolatile memory device including a plurality of erase units, and a memory controller. Each of the plurality of erase units include a plurality of memory cells. The memory controller is configured to assign first memory cells of each of first erase units among the plurality of erase units as y-level cells, assign second memory cells of each of second erase units among the plurality of erase units as x-level cells, allocate a zone to at least one first erase unit among the first erase units and permit a sequential write with respect to the zone, buffer data to be written in the zone by using at least one second erase unit among the second erase units, and provide, to the external host device, information about the at least one second erase unit buffering the data to be written in the zone.