Memory System with Dual Buffers for Variable-Speed Writes
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Solution Overview
Problem
Existing memory systems face challenges in improving the efficiency and latency of write processes, particularly when handling multiple streams of data with varying write speeds, leading to increased garbage collection frequency and degraded write amplification.
Innovation Solution
The implementation of a memory system with a nonvolatile memory and a controller that utilizes a first and second write buffer with different capacities and bandwidths, classifying write commands into groups based on write speed, and allocating them to appropriate buffers (DRAM or SRAM) to manage write destination blocks efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single write buffer is used for all write commands, then the device structure is simple, but write processing efficiency deteriorates when handling multiple streams with varying write speeds
Solution Approach 1:
The write buffer is segmented into multiple buffers (first write buffer and second write buffer) with different capacities and bandwidths. Each buffer is optimized for specific write speed requirements, allowing efficient handling of multiple data streams with varying write speeds while maintaining manageable complexity through structured division.
Solution Approach 2:
Different buffers are assigned different local qualities (capacities and bandwidths) to match the specific requirements of different write command groups. Fast write commands use high-bandwidth buffers while slow write commands use high-capacity buffers, optimizing overall write processing efficiency without requiring all buffers to have uniform high performance.
2Loss of energy
If data is accumulated in the buffer until minimum write size is reached, then write amplification is reduced, but write latency increases for slow write speeds
Solution Approach 1:
The system dynamically selects between different buffer configurations based on the write speed characteristics of incoming commands. For slow write speeds, the system uses a buffer configuration that prioritizes reaching minimum write size to reduce write amplification. For fast write speeds, it uses a configuration that prioritizes lower latency by not waiting for minimum size accumulation. This dynamic adaptation resolves the contradiction between write amplification and latency.
3Reliability
If the buffer capacity is increased to handle all write commands, then buffer overflow is prevented, but the cost and complexity of the memory system increases
Solution Approach 1:
The buffer system is segmented into multiple buffers with different capacities. The first write buffer has a larger capacity optimized for slow write speeds, while the second write buffer has a smaller capacity optimized for fast write speeds. This segmentation prevents buffer overflow for different command types without requiring a single excessively large buffer, thereby controlling complexity and cost.
Solution Approach 2:
The multiple buffers work together as a unified buffer system that handles all types of write commands. Each buffer serves specific functions based on write speed characteristics, but collectively they provide universal coverage for all write operations, preventing overflow across different scenarios without requiring each individual buffer to be maximally sized.
4Productivity
If write commands are processed sequentially, then the control logic is simple, but write throughput decreases when multiple streams are present
Solution Approach 1:
Write commands are segmented into different groups based on their write speed characteristics. The controller classifies incoming write commands into first group (slow write speed) and second group (fast write speed), directing each group to appropriate buffers. This segmentation enables parallel processing of different command types, increasing throughput while keeping classification logic manageable through clear speed-based categorization.
Data Source
AI summary
According to one embodiment, a memory system includes a nonvolatile memory, a first write buffer, a second write buffer having a capacity smaller than that of the first write buffer and a bandwidth larger than that of the first write buffer, and a controller. When the write speed of the first group is less than a first value, the controller loads unloaded data among first data into the first write buffer, and after an amount of the first data reaches or exceeds a minimum write size, writes the first data to a first write destination block. When the write speed of the second group is greater than or equal to the first value, the controller loads second data having the minimum write size into the second write buffer and writes the second data to the second write destination block.