SSD RAM Mass Storage via Power Loss Protection

Solution Overview

Problem

Solid-state drives (SSDs) face challenges in managing metadata storage, as NAND-type memory cells wear out quickly when used for continuously updated data, and nonvolatile RAM adds cost and size without increasing user data capacity.

Innovation Solution

Incorporating a flash memory device, a power loss protection circuit, and a controller that directs I/O requests to either the flash memory or RAM, allowing RAM to function as a mass storage device, with a mapping table to manage logical block addresses and perform read/write operations, and a power loss protection circuit to ensure data integrity during power interruptions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If nonvolatile RAM is used to store metadata, then data integrity during power loss is ensured, but cost and device size increase without increasing user data capacity

Engineering Contradiction:

Improvedata integrityVSAvoiddevice size

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent makes the RAM device perform dual functions: serving as both metadata storage during normal operation and as user-accessible mass storage capacity. By configuring the RAM as a separate mass storage device visible to external computing devices, the same hardware component provides both reliability benefits (through power loss protection for metadata) and additional storage capacity, eliminating the need for separate nonvolatile RAM dedicated solely to metadata storage.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Device complexity

If NAND memory cells are used to store continuously updated metadata, then device size is reduced, but the memory cells wear out quickly

Engineering Contradiction:

Improvedevice sizeVSAvoidmemory cell durability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent extracts the metadata storage function from the NAND flash memory device and relocates it to a separate RAM device with power loss protection circuitry. This separation prevents the wear-induced reliability degradation that would occur if NAND cells were used for continuously updated metadata, while the extracted RAM component can be configured as additional mass storage capacity rather than merely internal metadata storage.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If RAM is configured as nonvolatile with power loss protection, then metadata loss is prevented, but additional cost is incurred

Engineering Contradiction:

Improvemetadata retentionVSAvoidcost

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent makes the RAM device perform dual functions: serving as both metadata storage during normal operation and as user-accessible mass storage capacity. By configuring the RAM as a separate mass storage device visible to external computing devices, the same hardware component provides both reliability benefits (through power loss protection for metadata) and additional storage capacity, eliminating the need for separate nonvolatile RAM dedicated solely to metadata storage.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS10824344B2Solid-state drive with non-volatile random access memory

Publication Date: 2020.11.03 KIOXIA CORP

AI summary

A solid-state drive includes a flash memory device, a power loss protection circuit, a dynamic random access memory (RAM) coupled to the power loss protection circuit, and a controller configured to direct I/O requests to either the flash memory drive or the RAM. Because the controller can direct I/O request to the RAM, the RAM is revealed as a separate mass storage device to a host. Consequently, the RAM provides additional and significantly higher performance storage capacity to the solid-state drive.