Block Storage Metadata Persistence via Data Plane Key-Value Stores

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Solution Overview

Problem

The interdependency among control plane components in block storage systems can lead to cascading failures, reducing the availability and durability of the system, as the unavailability of one component can prevent downstream components from functioning, especially during replica placement and migration processes.

Innovation Solution

Persisting metadata associated with volumes in the data plane, rather than the control plane, using key-value stores on block storage servers, allows the placement component to determine suitable storage servers without relying on other control plane components, ensuring continued functionality even during control plane outages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If control plane components are highly interdependent to enable coordinated management of block storage resources, then system control capability is improved, but system availability deteriorates due to cascading failures

Engineering Contradiction:

Improvesystem control capabilityVSAvoidsystem availability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent segments the control plane metadata into multiple independent key-value stores distributed across different block storage servers. Instead of having all control plane components depend on a centralized metadata service, the metadata is divided and stored independently, allowing the system to maintain control functionality even when individual key-value stores or control plane components fail.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces key-value stores as intermediary components between the control plane and block storage servers. These key-value stores act as mediators that decouple the direct dependencies between control plane components, allowing them to interact through standardized key-value operations rather than direct component-to-component communication, thereby reducing cascading failure risks.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If metadata is stored in the control plane to enable centralized management, then coordination among components is improved, but failure propagation increases during control plane outages

Engineering Contradiction:

Improvecoordination capabilityVSAvoidfailure propagation

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent extracts critical metadata (such as replica placement information) from the control plane and stores it directly in the data plane on block storage servers. This extraction removes the single point of failure in the control plane metadata storage, allowing block storage servers to access essential metadata independently even when the control plane is unavailable, thereby preventing failure propagation.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent performs preliminary action by pre-storing metadata about replica placement and volume information in key-value stores on block storage servers before control plane operations are needed. This advance preparation ensures that when control plane outages occur, servers already have the necessary information cached locally to continue operations without waiting for control plane responses.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If control plane components have multiple dependencies to achieve comprehensive resource management, then management completeness is improved, but operational continuity deteriorates during component failures

Engineering Contradiction:

Improvemanagement completenessVSAvoidoperational continuity

Core Design Contradiction:

Adaptability or versatilityVSDuration of action of stationary object

Solution Approach 1:

The patent enables block storage servers to serve themselves by storing essential metadata locally in key-value stores. Instead of requiring continuous interaction with control plane components for metadata access, servers can independently retrieve placement information, volume metadata, and replica information from their local key-value stores, maintaining operational continuity during control plane outages.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS11237747B1Arbitrary server metadata persistence for control plane static stability

Publication Date: 2022.02.01 AMAZON TECH INC

AI summary

Systems and methods are disclosed for reducing interdependency among control plane on a block storage system. Embodiments described herein can implement a key-value data store on the data plane servers. In one embodiment, the key-value store stores data regarding placement constraints and enables the block storage system to make placement decisions without control plane dependencies. In another embodiment, the key-value store persisted by the data plane enable the block storage system to migrate volumes while maintaining performance settings.