Nonvolatile Memory Controller Zone Buffer Allocation

Solution Overview

Problem

Existing memory systems, such as solid state drives (SSDs) with NAND flash memory, face challenges in efficiently utilizing storage regions of nonvolatile memories, particularly in managing write operations across multiple zones with varying write speeds.

Innovation Solution

The memory system employs a controller that allocates storage regions to zones and switches between two modes of operation. In the first mode, write operations are focused on a specific zone until a predetermined time elapses after an erase operation. If the zone remains partially empty, the controller transitions to a second mode, where the storage region is used as a shared nonvolatile buffer for all zones, allowing write data from any zone to be stored there.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the controller writes data to a specific zone immediately after erase operation, then the storage region utilization is improved, but the write operation time is extended when write speed is slow

Engineering Contradiction:

Improvestorage region utilization efficiencyVSAvoidwrite operation time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The controller performs preliminary actions by switching to the second mode of operation before completing all write operations. When the zone remains partially empty after a predetermined time, the controller proactively transitions to using the storage region as a shared buffer, preparing for future write operations from any zone rather than waiting for the current zone to be fully written.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically switches between two operational modes based on real-time conditions. The controller monitors whether a zone is fully written after erase operations and dynamically transitions between first mode (zone-specific writing) and second mode (shared buffer operation), adapting the writing strategy to current storage state and write speed conditions.

Inventive Principle:

Principle #15Dynamics

2Loss of time

If the controller uses a storage region as a shared buffer for all zones, then the time required for storage block to become fully written is reduced, but the zone-specific write focus is lost

Engineering Contradiction:

Improvetime required for storage block to become fully writtenVSAvoidzone-specific write operation control

Core Design Contradiction:

Loss of timeVSEase of operation

Solution Approach 1:

The system dynamically switches between two operational modes based on real-time conditions. The controller monitors whether a zone is fully written after erase operations and dynamically transitions between first mode (zone-specific writing) and second mode (shared buffer operation), adapting the writing strategy to current storage state and write speed conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The controller changes operational parameters by switching between different writing modes. In the first mode, the storage region is dedicated to a specific zone with zone-specific write control. In the second mode, the storage region becomes a shared buffer where write operations can be performed from any zone, fundamentally changing the parameter of write operation scope based on system state.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the controller waits for a zone to be fully written before switching modes, then the write operation completeness is ensured, but the storage region efficiency is reduced

Engineering Contradiction:

Improvewrite operation completenessVSAvoidstorage region efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The controller performs preliminary actions by switching to the second mode of operation before completing all write operations. When the zone remains partially empty after a predetermined time, the controller proactively transitions to using the storage region as a shared buffer, preparing for future write operations from any zone rather than waiting for the current zone to be fully written.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The controller continuously monitors the write operation status and storage region state, using feedback to determine when to switch modes. The predetermined time threshold and partial empty condition serve as feedback mechanisms that trigger mode transitions, allowing the system to adapt based on actual write progress rather than fixed completion criteria.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS20250147698A1Memory system and method of controlling nonvolatile memory

Publication Date: 2025.05.08 KIOXIA CORP

AI summary

According to one embodiment, a controller of a memory system executes a first write operation of writing write data into a first storage region, in response to reception of one or more write requests for specifying a first zone from a host, during a period from execution of an erase operation of the first storage region until a first time elapses. When the first time has elapsed after execution of the erase operation, in a state in which an unwritten region having a size larger than or equal to a first size remains in the first storage region, the controller does not execute the first write operation, allocates the first storage region as a nonvolatile buffer capable of temporarily storing write data to be written to each of a plurality of zones.