Memory Controller IZG Migration for ZNS Write Amplification
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Solution Overview
Problem
Conventional memory sub-systems face inefficiencies in data migration from single-level cell (SLC) storage to quad-level cell (QLC) storage, leading to increased write amplification, reduced endurance of SLC, and prolonged operations due to sequential migration based on host completion.
Innovation Solution
A memory controller is configured to intelligently and dynamically migrate data by dividing zones into internal zone groups (IZGs) and using separate write cursors for each IZG, allowing for non-sequential migration based on the number of zones ready for migration in each IZG.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sequential migration based on host completion is used, then data migration from SLC to QLC storage is performed, but write amplification increases and SLC endurance decreases
Solution Approach 1:
The patent divides zones into internal zone groups (IZGs) and uses separate write cursors for each IZG, enabling parallel tracking of multiple zones. This segmentation allows the system to identify and migrate ready zones without waiting for sequential host completion, reducing write amplification while maintaining SLC endurance through optimized migration timing.
Solution Approach 2:
The patent implements dynamic migration decision-making by continuously monitoring zone completion status across multiple IZGs. The system dynamically selects which zones to migrate based on real-time readiness status rather than following a fixed sequential order, optimizing the balance between write amplification and SLC endurance.
2Productivity
If sequential migration based on host completion is used, then data migration is performed, but operation duration is prolonged
Solution Approach 1:
The patent performs preliminary tracking of zone completion status across multiple IZGs using separate write cursors. By maintaining readiness information in advance, the system can immediately initiate migration when zones are ready without waiting for sequential host completion signals, significantly reducing operation duration while improving migration throughput.
Solution Approach 2:
The patent enables continuous migration operations by monitoring multiple IZGs simultaneously and migrating zones as soon as they are ready. This eliminates idle waiting periods between migrations and maintains continuous useful action, improving overall productivity without extending total operation duration.
3Productivity
If separate write cursors and internal zone groups are used, then migration order is optimized, but system complexity increases
Solution Approach 1:
The patent segments zones into IZGs with dedicated write cursors, which initially appears to increase complexity. However, this segmentation simplifies the migration decision logic by organizing zones into manageable groups with tracked readiness status, making the overall system more efficient and maintainable despite the additional structural elements.
Data Source
AI summary
The disclosure configures a memory sub-system controller to efficiently perform block migration (e.g., from SLC cache to QLC blocks) in a Zone Namespace (ZNS) device. The controller associates a plurality of zones of the set of memory components with a plurality of internal zone groups (IZGs) each associated with a different write cursor. The controller programs data to a first portion of a set of memory components using the plurality of write cursors, the first portion being associated with a first type of storage, and determines that an individual IZG of the plurality of IZGs satisfies a migration criterion. The controller migrates a portion of the data stored in the first portion of the set of memory components corresponding to the individual IZG to a second portion of the set of memory components, the second portion of the set of memory components being associated with a second type of storage.