Accelerated Non-Volatile Memory Recirculation via Coarse Fine Lookup
Solution Overview
Problem
Conventional NAND Flash-based SSDs face inefficiencies in garbage collection due to the need to individually examine every physical location within a block to determine valid logical pages, leading to high processing power requirements and prolonged garbage collection times.
Innovation Solution
Implementing a method that includes a coarse page lookup to identify valid logical pages and a fine page lookup to verify their validity, allowing for accelerated non-volatile memory recirculation by processing recirculation commands efficiently across physical pages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional garbage collection examines every physical location individually to determine valid logical pages, then measurement precision is improved, but processing time and power consumption increase significantly
Solution Approach 1:
The patent segments the garbage collection process into two distinct phases: a coarse phase that quickly identifies candidate valid logical pages using block-level metadata, and a fine phase that verifies these candidates with precise page-level checks. This segmentation allows the system to avoid examining every physical location individually while maintaining accurate identification of valid pages, thereby reducing garbage collection time without sacrificing measurement precision.
2Measurement precision
If conventional garbage collection examines every physical location individually to determine valid logical pages, then measurement precision is improved, but processing power requirements increase
Solution Approach 1:
The patent divides the processing workload into two segments: the coarse phase uses minimal processing power to filter out obviously invalid pages based on block metadata, and the fine phase concentrates processing power only on verifying the remaining candidate pages. This segmentation dramatically reduces the total processing power required compared to examining every physical location with full verification, while still achieving accurate identification of valid logical pages.
3Productivity
If garbage collection is deferred to maximize invalidated data in block, then productivity is improved, but device complexity increases due to need for tracking and management
Solution Approach 1:
The patent implements preliminary action by maintaining block-level metadata that tracks the validity status of logical pages in advance of garbage collection needs. This preliminary tracking structure allows the system to defer garbage collection until blocks are fully invalidated, maximizing productivity benefits, while the metadata infrastructure provides an organized framework that manages the complexity of tracking multiple logical pages across physical blocks.
Data Source
AI summary
A method, according to one embodiment, includes: receiving a recirculation command; performing a coarse page lookup to determine valid ones of logical pages to be recirculated; requesting performance of a fine page lookup on source physical addresses containing the valid logical pages to verify the valid logical pages; and sending write commands corresponding to verified valid logical pages from the fine page lookup. Other systems, methods, and computer program products are described in additional embodiments.