Pre-emptive Garbage Collection for Flash Memory Write Stability

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Solution Overview

Problem

Flash memory systems face performance degradation due to fragmentation, which affects transfer speed during garbage collection operations, especially during Speed Class tests, as conventional garbage collection methods can negatively impact sequential write performance.

Innovation Solution

Implementing pre-emptive garbage collection methods, such as the 'least work to do' or 'least recently used' algorithms, to proactively manage garbage collection operations, ensuring that a predetermined threshold of garbage collection is performed during data writes, thereby maintaining optimal sequential write performance and meeting Speed Class specifications.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If conventional garbage collection is performed during Speed Class tests, then memory fragmentation is reduced, but sequential write performance deteriorates

Engineering Contradiction:
Improvememory fragmentationVSAvoidsequential write performance
Core Design Contradiction:
Stability of the object's compositionVSProductivity

Solution Approach 1:

The patent applies preliminary action by performing garbage collection before the Speed Class test begins, rather than during the test. The controller identifies candidate blocks for garbage collection and prepares them in advance, ensuring that when the Speed Class test executes sequential writes, the garbage collection process will not interfere with and degrade the measured write performance.

Inventive Principle:
Principle #10Preliminary action

2Speed

If garbage collection is performed proactively, then transfer speed is maintained, but device complexity increases

Engineering Contradiction:
Improvetransfer speedVSAvoiddevice complexity
Core Design Contradiction:
SpeedVSDevice complexity

Solution Approach 1:

The patent implements self-service by enabling the memory controller to autonomously monitor its own operational state, identify when garbage collection is needed, and execute the garbage collection process without external intervention. The controller tracks block usage patterns and automatically initiates garbage collection of candidate blocks when appropriate, maintaining transfer speed while avoiding the need for additional hardware components or complex external control mechanisms.

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP2588962B1Pre-emptive garbage collection of memory blocks
Publication Date: 2020.03.18 SANDISK TECHNOLOGIES LLC
  • EP2588962B1 patent drawingFigure 1
  • EP2588962B1 patent drawingFigure 2~3
  • EP2588962B1 patent drawingFigure 4~5

AI summary

A method and system pre-emptively perform garbage collection operations of a forced amount on update blocks in a memory device. The amount of garbage collection needed by a certain data write is monitored and adjusted to match the forced amount if necessary. Update blocks may be selected on the basis of their recent usage or the amount of garbage collection required. Another method and system may store control information about update blocks in a temporary storage area so that a greater number of update blocks are utilized. The sequential write performance measured by the Speed Class test may be optimized by using this method and system.