Hybrid SLC MLC Flash Drive Data Placement

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Solution Overview

Problem

Conventional SSDs using only SLC flash memory are expensive and lack storage density, while those using only 2-bit or 3-bit MLC flash memory are slower, more power-intensive, and less reliable compared to SLC flash memory.

Innovation Solution

Implementing a flash memory drive that combines SLC and MLC flash memory, where hot data is stored in SLC flash memory for faster access and cold data in MLC flash memory, optimizing storage costs and performance by dynamically moving data between the two based on access frequency and idle times.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If only SLC flash memory is used in SSD, then write speed and reliability are improved, but cost increases and storage density decreases

Engineering Contradiction:

Improvewrite reliabilityVSAvoidstorage density

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The flash memory storage is segmented into two distinct types: SLC flash memory for hot data and MLC flash memory for cold data. This segmentation allows each type to be optimized for its specific purpose, with SLC providing reliability for frequently accessed data and MLC providing high storage density for less frequently accessed data, thereby resolving the contradiction between reliability and storage density.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different quality characteristics are applied to different parts of the storage system: SLC flash memory with high reliability characteristics is allocated for hot data, while MLC flash memory with high storage density characteristics is allocated for cold data. This local quality differentiation resolves the contradiction by ensuring each data type is stored in the most appropriate medium.

Inventive Principle:

Principle #3Local quality

2Quantity of substance

If only MLC flash memory is used in SSD, then storage density increases and cost decreases, but write speed and reliability worsen

Engineering Contradiction:

Improvestorage densityVSAvoidwrite reliability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The storage system is segmented into SLC and MLC regions, allowing MLC to provide high storage density while SLC provides high reliability for critical hot data. This segmentation resolves the contradiction by ensuring that data requiring high reliability is stored in SLC while maximizing overall storage density through MLC.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

High reliability quality is locally applied to hot data stored in SLC flash memory, while high storage density quality is locally applied to cold data stored in MLC flash memory. This local quality assignment resolves the contradiction between storage density and reliability.

Inventive Principle:

Principle #3Local quality

3Productivity

If hot data is stored in SLC flash memory, then write speed improves, but storage cost increases

Engineering Contradiction:

Improvewrite speedVSAvoidstorage cost

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

High write speed quality is locally applied only to hot data stored in SLC flash memory, while cost-effective storage is used for cold data in MLC flash memory. This local quality differentiation resolves the contradiction by ensuring high write speed is provided only where necessary for frequently accessed data, minimizing overall cost.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The storage system is segmented into hot data and cold data regions, with hot data stored in expensive but fast SLC and cold data stored in cheaper MLC. This segmentation resolves the contradiction by limiting the use of expensive high-speed storage to only the portion of data that requires it.

Inventive Principle:

Principle #1Segmentation

4Quantity of substance

If cold data is stored in MLC flash memory, then storage cost decreases, but access speed worsens

Engineering Contradiction:

Improvestorage costVSAvoidaccess speed

Core Design Contradiction:

Quantity of substanceVSSpeed

Solution Approach 1:

Cost-effective storage quality is locally applied to cold data in MLC flash memory, while high-speed access quality is locally applied to hot data in SLC flash memory. This local quality assignment resolves the contradiction by ensuring low-cost storage is used only for data that does not require fast access.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The storage system is segmented into hot data and cold data regions, with cold data stored in low-cost MLC and hot data stored in high-speed SLC. This segmentation resolves the contradiction by isolating cold data in cost-effective storage while maintaining fast access for hot data.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS10854290B1Utilizing a flash memory drive which includes single-level cell flash memory and multi-level cell flash memory

Publication Date: 2020.12.01 EMC IP HLDG CO LLC

AI summary

A technique manages data in a flash memory drive which includes single-level cell (SLC) flash memory and multi-level cell (MLC) flash memory. The technique involves performing, within the flash memory drive, data placement operations on data which has been written to the flash memory drive. The technique further involves, based on the data placement operations, storing hot data in the SLC flash memory. The technique further involves, based on the data placement operations, storing cold data in the MLC flash memory, the hot data being accessed more frequently than the cold data. Such hot data and cold data can be distinguished based on access frequency.