Persistent Memory Journaling Across DRAM and NVM Tiers

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Solution Overview

Problem

Conventional NVDIMMs with auxiliary power sources, such as batteries or supercapacitors, face high material and operational costs, limited lifespan, and time-consuming full save-to-FLASH operations during power failures, leading to potential system vulnerabilities and increased maintenance needs.

Innovation Solution

A multi-tier memory scheme that divides write streams among DRAM, faster non-volatile memory (NVM) for journaling, and slower NVM for image storage, using journaling to track data change units and periodically update the base image, reducing the need for large auxiliary power sources and minimizing data loss during power failures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If auxiliary power sources (batteries or supercapacitors) are used in conventional NVDIMMs, then data persistence during power failures is improved, but material costs and operational costs increase significantly

Engineering Contradiction:

Improvedata persistence during power failureVSAvoidmaterial cost

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent extracts and removes the auxiliary power source component from the NVDIMM system entirely. Instead of using batteries or supercapacitors, the invention relies on the inherent non-volatility of NVM to persist data without requiring additional power storage components, thereby eliminating material costs while maintaining data persistence reliability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces expensive long-lifespan auxiliary power sources with a cost-effective NVM-based persistence mechanism. The NVM media serves as a disposable-like component that can be periodically updated without requiring the complex, expensive, and maintenance-intensive auxiliary power infrastructure

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If auxiliary power sources are used in conventional NVDIMMs, then data persistence is improved, but the lifespan of the system is limited by the auxiliary power source

Engineering Contradiction:

Improvedata persistence during power failureVSAvoidsystem lifespan

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

By removing the auxiliary power source, the patent eliminates the lifespan limitation imposed by battery or supercapacitor degradation. The system now relies on the much longer lifespan of NVM components and DRAM, extending overall system durability without maintenance concerns related to power source replacement

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent implements periodic save-to-NVM operations that proactively persist data before power failures can occur. This preliminary action ensures data is safely stored in non-volatile media without requiring auxiliary power sources to maintain data during outages, thereby extending system operational lifespan

Inventive Principle:

Principle #10Preliminary action

3Reliability

If full save-to-FLASH operations are performed during power failures, then data persistence is ensured, but system downtime increases significantly

Engineering Contradiction:

Improvedata persistence during power failureVSAvoidsystem downtime

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements periodic save-to-NVM operations that occur at scheduled intervals during normal operation. This periodic action ensures data is progressively persisted over time without requiring large-scale operations during power failures, thereby minimizing system downtime while maintaining data persistence reliability

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

Data is proactively saved to NVM during normal operation before power failures occur. This preliminary action ensures that when power failures happen, the system can recover quickly with minimal downtime since data has already been persisted to non-volatile media

Inventive Principle:

Principle #10Preliminary action

4Reliability

If conventional NVDIMM architecture with auxiliary power sources is used, then data persistence is improved, but maintenance needs and system vulnerability increase

Engineering Contradiction:

Improvedata persistence during power failureVSAvoidmaintenance needs

Core Design Contradiction:

ReliabilityVSEase of repair

Solution Approach 1:

The patent removes the auxiliary power source subsystem, eliminating the maintenance burden associated with battery or supercapacitor replacement. The simplified architecture using only DRAM and NVM components reduces system vulnerability and maintenance needs while maintaining data persistence through periodic save operations

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The NVM-based persistence mechanism operates autonomously without requiring external power sources or complex control logic. The system self-manages data persistence through periodic save operations, reducing maintenance complexity and eliminating vulnerabilities associated with auxiliary power source failures

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS12579042B2High performance persistent memory

Publication Date: 2026.03.17 RAMBUS INC

AI summary

The embodiments described herein describe technologies for non-volatile memory persistence in a multi-tiered memory system including two or more memory technologies for volatile memory and non-volatile memory.