Host Controlled Flexible Data Layout for SSD Garbage Collection
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Solution Overview
Problem
Existing SSD designs face limitations in garbage collection efficiency due to block-based IO interfaces, which hinder optimized data placement and increase storage costs.
Innovation Solution
The technology enables fine-grained drive placement functionality by allowing hosts to select placement identifiers that uniquely identify combinations of parallel units and reclaim unit streams, optimizing data placement for garbage collection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If block-based IO interface is used, then compatibility with existing hard drive interfaces is maintained, but garbage collection efficiency is limited
Solution Approach 1:
The storage device is divided into multiple parallel units, each containing multiple reclaim unit streams. This segmentation allows the host to selectively place data in specific reclaim units across different parallel units, enabling fine-grained data placement control that improves garbage collection efficiency while maintaining block-based IO compatibility.
Solution Approach 2:
The invention introduces a new dimensional structure with placement identifiers that map to specific combinations of parallel units and reclaim unit streams. This additional dimension of organization enables the host to optimize data placement for garbage collection without changing the fundamental block-based IO interface, thus improving GC efficiency while maintaining interface compatibility.
2Productivity
If host software manages NAND memory operations directly, then data placement optimization is achieved, but device complexity increases
Solution Approach 1:
The storage device introduces an intermediary layer of management for NAND operations. The device maintains control over NAND-level operations such as wear leveling, retention compensation, and read-disturb compensation, while exposing a simplified interface to the host for data placement. This intermediary layer absorbs the complexity of NAND management, allowing the host to achieve optimization without directly handling complex NAND operations.
3Ease of operation
If flash translation table is maintained on host software, then direct NAND management is enabled, but performance bottleneck occurs due to serialized updates
Solution Approach 1:
The flash translation table is segmented and distributed across multiple parallel units and reclaim unit streams. This segmentation allows concurrent updates in different regions without serializing all operations at a single point, thereby improving update performance while maintaining the ability for direct NAND management through the placement identifier system.
4Productivity
If fine-grain placement control is implemented, then garbage collection optimization is achieved, but compatibility with virtual machine interface boundaries is lost
Solution Approach 1:
The storage device is segmented into multiple parallel units and reclaim unit streams that can be independently managed. This segmentation enables fine-grained placement control for garbage collection optimization while maintaining the ability to present storage to virtual machines through standardized interfaces, as the segmentation occurs at the device level rather than at the virtualization boundary.
Data Source
AI summary
A drive placement or placement functionality can enable initial copies of data to be placed on a drive in reclaim unit (HRUs) in a manner which is probabilistically more efficient from a garbage collection (GC) perspective and leverages knowledge of a host or application using the data. The placement functionality enables the advantages of fine-grained placement functionality while simultaneously allowing a storage device or storage drive to maintain NAND or other management responsibility, and not allocate that responsibility to an application or host device using the device.