Zone-Based Flash Storage Mapping for Lower Write Amplification
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Solution Overview
Problem
The repetitive write operations in nonvolatile memory devices, particularly flash memory, lead to reduced lifetime and reliability due to the erase-before-write characteristic, which increases the write amplification factor (WAF) and affects data security.
Innovation Solution
Implementing a storage device with a nonvolatile memory device comprising multiple storage regions, including a first storage region for user data, a second storage region for a file system, a third storage region for a map table, and a fourth storage region for buffering, along with a memory controller that manages these regions to perform zone-based data management, including sequential writing, garbage collection, and partial invalidation to reduce WAF and enhance security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If write operations are performed in nonvolatile memory, then data storage is achieved, but the lifetime and reliability of the memory are reduced due to erase-before-write characteristic
Solution Approach 1:
The memory space is divided into multiple zones (first zone for sequential writing, second zone for random writing, third zone for buffer). This segmentation allows different writing strategies to be applied to different zones, reducing the impact of erase-before-write operations on overall memory lifetime while maintaining write productivity.
Solution Approach 2:
A buffer zone is introduced as an intermediary between the host and the main storage zones. The buffer temporarily stores write data before it is moved to the main storage zones, allowing write operations to be decoupled from erase operations and reducing write amplification.
2Reliability
If garbage collection operations are performed frequently, then data security is improved through partial invalidation, but the write amplification factor increases
Solution Approach 1:
Instead of performing full garbage collection on entire zones, the system performs partial invalidation only on specific pages or blocks where data security is concerned. This partial action approach maintains data security while significantly reducing the write amplification factor compared to full zone invalidation.
Solution Approach 2:
Different security levels and invalidation strategies are applied to different zones and pages within zones. The system can selectively invalidate data in specific regions based on security requirements, rather than applying uniform invalidation across the entire memory, thus reducing overall write amplification.
3Speed
If zone-based data management is implemented, then write speed is improved, but the device complexity increases due to multiple storage regions and management operations
Solution Approach 1:
The memory is segmented into zones with distinct purposes (sequential writing zone, random writing zone, buffer zone). Each zone has optimized management strategies, allowing high-speed writing in appropriate zones while simplifying the control logic for each segment compared to managing a single uniform memory space.
Solution Approach 2:
The system automatically manages data placement, movement, and invalidation across zones without requiring complex external intervention. The controller autonomously performs garbage collection, buffer management, and zone allocation, reducing the complexity burden on the host system while maintaining high write speeds.
Data Source
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AI summary
Disclosed is a storage device which includes a nonvolatile memory device that includes a plurality of erase units each including a plurality of memory cells, and a memory controller. Based on an open zone request received from an external host device, the memory controller allocates a zone to at least one erase unit among the plurality of erase units and permits only a sequential write with respect to the zone. The memory controller generates a map table mapping sequential logical addresses of data written in the zone to sequential physical addresses. Based on a partial invalidation request received from the external host device, the memory controller manages data corresponding to the partial invalidation request from among the data written in the zone as invalid data while maintaining the map table.