SSD Power-Loss Data Integrity via Metadata Segmentation

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Solution Overview

Problem

Conventional Solid State Drives (SSDs) face data integrity issues due to insufficient power from Power-Loss-Protection (PLP) capacitors during sudden power loss, leading to potential data loss and the need for costly, space-inefficient additional capacitors, which also introduce additional failure points.

Innovation Solution

The SSD stores only the write commands in non-volatile storage using PLP capacitors during a power loss event, marking associated storage locations as uncorrectable upon power restoration, thereby reducing the amount of data to be stored and the required backup power, allowing for a decrease in the number and size of PLP capacitors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If PLP capacitors are used to write all inflight data to non-volatile storage during power loss, then data integrity is improved, but cost and space requirements increase significantly

Engineering Contradiction:

Improvedata integrityVSAvoidPLP capacitor size and cost

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent segments the data protection function into two parts: (1) storing only metadata (write commands and logical-to-physical address mappings) in non-volatile storage during power loss, and (2) maintaining a separate data structure (L2P table) that can be reconstructed after power restoration. This segmentation allows protection of data integrity without requiring capacitors large enough to save all inflight data, thus resolving the contradiction between reliability and quantity of substance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary action by pre-storing the metadata structure (write commands and L2P mappings) in non-volatile storage before power loss occurs. When power is restored, this pre-stored metadata enables rapid reconstruction of the data integrity verification structure without requiring the capacitors to hold all inflight data during the outage, thereby reducing capacitor size while maintaining reliability.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If additional PLP capacitors are added to provide sufficient backup power, then data integrity during power loss is improved, but device complexity and failure points increase

Engineering Contradiction:

Improvedata integrityVSAvoidnumber of capacitors and failure points

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the essential elements needed for data integrity verification (write commands and L2P mappings) from the complete inflight data set. By storing only this extracted metadata in non-volatile storage during power loss, the system achieves data integrity protection without requiring additional capacitors, thereby reducing device complexity and failure points while maintaining reliability.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If PLP capacitors are used to protect all inflight data, then data integrity is improved, but space occupancy in SSD increases

Engineering Contradiction:

Improvedata integrityVSAvoidcapacitor space in SSD

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent segments the protection scope to only include metadata (write commands and L2P mappings) rather than all inflight data. This segmentation dramatically reduces the energy storage requirement during power loss, allowing the use of smaller capacitors that occupy less space in the SSD while still ensuring data integrity through the reconstructed L2P table verification process.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent creates a simplified copy of the data structure (metadata including write commands and L2P mappings) that can be stored in non-volatile storage with minimal power. This copying approach allows integrity verification without requiring the full inflight data set, reducing capacitor size and space occupancy while maintaining reliability.

Inventive Principle:

Principle #26Copying

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach ensures that out-of-date data is not provided to the host after a power loss, significantly reducing the need for backup power and capacitors, improving cost, space efficiency, and reducing failure points while maintaining data integrity.

Implementation Method 1

The PLP capacitors may not have sufficient power to write all of the inflight data stored in the volatile storage to the non-volatile storage

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS11966295B2Capacitor energy management for unexpected power loss in datacenter SSD devices

Publication Date: 2024.04.23 KIOXIA CORP

AI summary

Various implementations described herein relate to systems and methods for a Solid State Drive (SSD) to manage data in response to a power loss event, including writing data received from a host to a volatile storage of the SSD, detecting the power loss event before the data is written to a non-volatile storage of the SSD, storing the write commands to a non-volatile storage of the SSD, marking at least one storage location of the SSD associated with the write commands as uncorrectable, for example, after the power is restored.