RAID SSD Check Data Caching for Lower Latency and NAND Wear

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Solution Overview

Problem

The existing RAID systems using solid state drives (SSDs) face issues of high latency and reduced lifespan due to frequent read-modify-write processes and excessive programming/erasing cycles of NAND, which are exacerbated by the need for check data updates.

Innovation Solution

Utilizing the persistent memory region (PMR) of each SSD as a cache for check data, reducing the need for direct NAND access and leveraging its faster memory-level operations to enhance read/write performance and extend SSD lifespan.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If check data is stored in NAND flash memory, then data redundancy is achieved, but read/write latency increases due to multiple I/O operations

Engineering Contradiction:

Improvedata redundancyVSAvoidread/write latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent segments the storage system into two distinct parts: NAND flash memory for storing user data and a separate cache memory for storing check data. This segmentation allows check data operations to be performed in the faster cache memory rather than in the slower NAND flash memory, thereby reducing read/write latency while maintaining data redundancy through the separated check data storage.

Inventive Principle:

Principle #1Segmentation

2Reliability

If check data is frequently updated in NAND, then data integrity is maintained, but programming/erasing cycles are consumed rapidly

Engineering Contradiction:

Improvedata integrityVSAvoidSSD lifespan

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent introduces a cache memory as an intermediary between the host system and the NAND flash memory for check data storage. The cache memory handles frequent check data updates, acting as a buffer that protects the NAND flash memory from excessive programming/erasing cycles. This intermediary structure maintains data integrity through frequent check data updates while preserving SSD lifespan by isolating the NAND from direct update operations.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If read-modify-write process is performed for each write operation, then data consistency is ensured, but operation complexity and latency increase

Engineering Contradiction:

Improvedata consistencyVSAvoidoperation complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the read-modify-write process into two independent parts: user data operations in NAND flash memory and check data operations in cache memory. This segmentation simplifies the overall operation complexity by allowing check data to be updated in the faster cache memory without requiring complex coordinate operations with NAND flash memory, while still ensuring data consistency through the maintained relationship between user data and check data.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS12386565B2Method and device for data storage based on redundant array of independent disks

Publication Date: 2025.08.12 SAMSUNG ELECTRONICS CO LTD

AI summary

A method of data storage based on a redundant array of independent disks (RAID), where the RAID includes a plurality of solid state drives (SSD), each SSD including a persistent memory region (PMR) and a NAND, includes writing first data into the NAND, and writing first check data into the PMR. The first check data is check data related to the first data.