FTL Synchronization for Lower SSD Write Amplification

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Solution Overview

Problem

Existing storage architectures that stack a host Flash Translation Layer (FTL) on top of a drive FTL in NAND Flash memory devices increase write amplification instead of reducing it, leading to unnecessary resource waste and reduced SSD lifespan due to over-provisioning.

Innovation Solution

Implement FTL synchronization by synchronizing host FTL operations with drive FTL operations, using host band validity levels to optimize defragmentation and garbage collection processes, thereby aligning host and physical bands to minimize write amplification and over-provisioning.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a host FTL is stacked on top of a drive FTL in NAND Flash memory devices, then data management capability is improved, but write amplification increases

Engineering Contradiction:

Improvedata management capabilityVSAvoidwrite amplification

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent merges the host FTL and drive FTL into a unified synchronized FTL system. The host FTL and drive FTL are coordinated through synchronization mechanisms where the host FTL issues commands and the drive FTL executes them while maintaining consistent state information. This integration eliminates the independent operation of separate FTL layers that caused multiplicative write amplification, allowing the system to achieve enhanced data management capability without the penalty of increased write amplification.

Inventive Principle:

Principle #5Merging (Combining)

2Adaptability or versatility

If a host FTL is stacked on top of a drive FTL, then data management functionality is enhanced, but device complexity increases

Engineering Contradiction:

Improvedata management functionalityVSAvoidFTL layer structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent segments the FTL functionality into distinct but synchronized components: the host FTL handles high-level data management decisions and command issuance, while the drive FTL handles low-level NAND Flash operations and physical band management. This segmentation allows each layer to specialize in specific tasks, enhancing overall data management functionality while maintaining manageable complexity through clear separation of concerns and defined interfaces.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements feedback mechanisms where the drive FTL reports status information, validity levels, and operation results back to the host FTL. This feedback loop enables the host FTL to make informed decisions about data placement, garbage collection, and defragmentation operations. The synchronization protocol ensures that both FTL layers have consistent views of the system state, reducing complexity by eliminating the need for complex conflict resolution mechanisms.

Inventive Principle:

Principle #23Feedback

3Reliability

If over-provisioning is used to account for extra read/write/erase cycles, then SSD reliability is improved, but storage capacity is reduced

Engineering Contradiction:

ImproveSSD reliabilityVSAvoidstorage capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent enables the FTL system to self-manage wear leveling and reliability through synchronized operation. The host FTL and drive FTL work together to track valid data locations, manage garbage collection, and perform defragmentation operations that distribute wear evenly across all NAND Flash blocks. This self-service approach allows the system to maintain high reliability without requiring excessive over-provisioning, as the intelligent management of read/write/erase cycles extends NAND Flash lifespan while preserving maximum storage capacity.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS20250390252A1Reducing write amplification and over-provisioning using flash translation layer synchronization

Publication Date: 2025.12.25 SK HYNIX NAND PRODUCT SOLUTIONS CORP

AI summary

A host Flash Translation Layer (FTL) synchronizes host FTL operations with the drive FTL operations to reduce write amplification and over-provisioning. Embodiments of FTL synchronization map, at the host FTL software (SW) stack level, logical bands in which data is managed, referred to as host bands, to the physical bands on a drive where data is stored. The host FTL tracks validity levels of data managed in host bands to determine validity levels of data stored in corresponding physical bands, and optimizes defragmentation operations (such as garbage collection processes and trim operations) applied by the host FTL SW stack to the physical bands based on the tracked validity levels.