NVRAM Staging for Persistent Storage Write Reduction

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Solution Overview

Problem

Flash memory devices and other semiconductor-based persistent storage devices have limited endurance due to practical limits on the number of block erase cycles, leading to increased bit error rates and reduced reliability.

Innovation Solution

Incorporating a persistent storage device with both persistent storage blocks and NVRAM blocks, along with a storage controller that manages data writes and transfers between these blocks, allowing multiple writes to NVRAM blocks to be consolidated into a single write to a persistent storage block, thereby reducing the number of writes and block erase operations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple writes are performed directly to persistent storage blocks, then data is stored reliably, but the number of block erase cycles increases reducing device endurance

Engineering Contradiction:

Improvedata storage reliabilityVSAvoiddevice useful life

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent applies preliminary action by writing data to NVRAM blocks first before transferring to persistent storage. The NVRAM serves as a staging area where multiple writes can be accumulated and consolidated into fewer persistent storage operations, reducing wear while maintaining data reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces NVRAM as an intermediary between the host and persistent storage. This mediator allows writes to be buffered and consolidated before being transferred to persistent storage blocks, reducing the number of erase cycles while ensuring data is eventually stored reliably

Inventive Principle:

Principle #24Intermediary (Mediator)

2Duration of action of stationary object

If writes are consolidated to reduce persistent storage operations, then device endurance improves, but data transfer time may increase

Engineering Contradiction:

Improvedevice useful lifeVSAvoiddata transfer time

Core Design Contradiction:

Duration of action of stationary objectVSLoss of time

Solution Approach 1:

By performing preliminary writes to NVRAM which has faster write characteristics, the system prepares data for eventual persistent storage without immediately incurring the time cost of persistent storage writes. The consolidation transfer can be optimized and does not block subsequent writes to NVRAM

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses periodic or triggered transfers from NVRAM to persistent storage rather than immediate writes. This allows writes to be batched and transferred in optimized operations, reducing the overall time impact while maintaining device endurance

Inventive Principle:

Principle #19Periodic action

3Reliability

If writes are performed to persistent storage blocks, then data is stored permanently, but energy consumption increases

Engineering Contradiction:

Improvepermanent data storageVSAvoidwrite energy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent uses preliminary writes to NVRAM which consumes less energy per write operation. The data is then transferred to persistent storage in consolidated operations, reducing the total energy consumption while ensuring permanent storage through the eventual transfer to persistent blocks

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9501398B2Persistent storage device with NVRAM for staging writes

Publication Date: 2016.11.22 PALISADE TECH LLP

AI summary

A persistent storage device includes both persistent storage, which includes a set of persistent storage blocks, and NVRAM, and in particular a set of NVRAM blocks. The persistent storage device also typically includes a storage controller. The persistent storage device, in addition to responding to commands to write data directly to and to read data directly from persistent storage blocks is also configured to write data to specified NVRAM blocks (e.g., specified by a host NVRAM write command) and to transfer data from a specified NVRAM block to a specified persistent storage block. As a result, multiple writes to a particular persistent storage block can be replaced with multiple writes to an NVRAM block and a subsequent single write to the particular persistent storage block. This reduces the number of writes to persistent storage and also reduces the number of corresponding block erase operations.