Flash Translation Layer Hot-Cold Data Separation
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Solution Overview
Problem
The limited storage capacity of non-volatile storage mediums like flash memory requires improved memory management to optimize data storage and retrieval efficiency, particularly in managing hot and cold data spots that lead to uneven wear and high write amplification.
Innovation Solution
A method and system for data separation that identifies the temperature of data in memory blocks during write operations, selects a victim block based on temperature, moves data to a destination block, and assigns a sequence number to the destination block when full, thereby reducing write amplification through effective wear leveling and garbage collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If data is stored in flash memory blocks without temperature-based separation, then storage capacity is utilized, but write amplification increases and wear becomes uneven
Solution Approach 1:
The patent segments stored data into hot data and cold data based on temperature characteristics, maintaining separate mappings for each type. This segmentation allows differential management strategies where hot data blocks are preserved longer and cold data blocks are recycled earlier, thereby reducing unnecessary write amplification while ensuring uniform wear across all blocks
Solution Approach 2:
The patent introduces temperature as a new parameter for characterizing data blocks, enabling the system to make recycling decisions based on temperature rather than just validity status. By changing the parameter used for block selection from binary valid/invalid to continuous temperature-based metrics, the system optimizes both write amplification and wear distribution
2Device complexity
If all data blocks are treated equally for recycling, then storage management is simple, but hot blocks are unnecessarily recycled causing performance degradation
Solution Approach 1:
The patent divides the data storage space into hot data region and cold data region with separate mapping structures. Hot data blocks are identified and protected from premature recycling, while cold data blocks are efficiently managed. This segmentation increases management complexity slightly but dramatically improves data retrieval efficiency by preventing unnecessary recycling of hot blocks
Solution Approach 2:
The system automatically identifies and categorizes data blocks as hot or cold based on their access patterns and temperature characteristics, then applies appropriate recycling policies without external intervention. This self-service mechanism handles the increased complexity internally while presenting simple operations to the host system
3Quantity of substance
If cold data is not separated from hot data, then storage space is maximized, but wear leveling becomes ineffective
Solution Approach 1:
The patent implements separate mapping tables for hot data and cold data, allowing independent management of each category. This enables effective wear leveling by selectively recycling cold data blocks while preserving hot data blocks, thereby distributing wear evenly across all physical blocks without compromising storage space utilization
Solution Approach 2:
The patent applies different management qualities to different data regions: hot data regions receive protection from recycling to maintain performance, while cold data regions are actively managed for recycling to ensure wear leveling. This local differentiation of management quality achieves both goals simultaneously
Data Source
AI summary
A method of data separation includes receiving a host write command operation, identifying temperature of data contained in memory blocks during the host write command operation, selecting a victim block of the memory blocks based on the identified temperature, moving data from the victim block to a destination block, and assigning a sequence number to the destination block when the destination block is full.