Non-Volatile Memory Mapping Reconstruction via Index Page Age Comparison

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Solution Overview

Problem

During unclean shutdowns, non-volatile memory systems face inefficiencies in reconstructing logical-to-physical mappings due to outdated index pages, requiring a time-consuming scan of the entire memory, which can be costly in terms of time and resources.

Innovation Solution

The system leverages information from index pages by scanning their ages and comparing them with the ages of corresponding data pages to determine reliability, using reliable index pages to reconstruct mappings and scanning only younger data blocks when necessary, potentially utilizing context information and index pages to reduce the processing load.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the system scans the entire NVM to reconstruct logical-to-physical mappings after an unclean shutdown, then reliability of mapping reconstruction is improved, but time consumption and processing resources increase significantly

Engineering Contradiction:
Improvemapping reconstruction reliabilityVSAvoidrecovery time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent segments the NVM into multiple regions with different validation requirements. Index pages are validated separately from data pages using age comparison, allowing the system to identify valid mapping information without scanning the entire memory. This segmentation enables selective processing of only those regions that require full validation.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent implements preliminary validation of index pages by comparing their ages with corresponding data pages before shutdown. This preliminary action identifies which index pages are likely valid, allowing the system to skip full scanning of those regions during recovery. The age comparison metadata is prepared in advance to guide the reconstruction process.

Inventive Principle:
Principle #10Preliminary action

2Productivity

If the system uses index pages for mapping reconstruction, then processing speed is improved, but reliability deteriorates when index pages are outdated

Engineering Contradiction:
Improvemapping reconstruction speedVSAvoidmapping accuracy
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The patent implements a feedback mechanism where the system continuously compares the ages of index pages with their corresponding data pages. This feedback loop identifies outdated index pages that may contain stale mapping information, allowing the system to flag them for validation or replacement before they cause reliability issues during reconstruction.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The system performs preliminary validation of index pages by comparing their ages with data page ages before the shutdown occurs. This preliminary action identifies which index pages are current and reliable, allowing the system to use them confidently during reconstruction without sacrificing speed. Outdated index pages are identified in advance for potential updates or validation.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP2570927B1Handling unclean shutdowns for a system having non-volatile memory
Publication Date: 2018.04.25 APPLE INC
  • EP2570927B1 patent drawingFigure 1
  • EP2570927B1 patent drawingFigure 2
  • EP2570927B1 patent drawingFigure 3

AI summary

Systems and methods are disclosed for handling unclean shutdowns for a system having non-volatile memory ("NVM"). In some embodiments, the system can leverage from information obtained from index pages in order to efficiently reconstruct logical-to-physical mappings after an unclean shutdown event. In other embodiments, the system can reconstruct logical-to-physical mappings by leveraging from context information stored in a NVM. In further embodiments, context information can be used in conjunction with index pages to reconstruct logical-to-physical mappings after an unclean shutdown.