Multi-tier Control Plane for Data Storage Systems
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Solution Overview
Problem
Existing block-based storage systems face challenges in maintaining data durability and low latency due to single-point failures in server nodes or control planes, leading to significant storage capacity unavailability and high recovery latencies across multiple locations.
Innovation Solution
A data storage system with a rack-mounted configuration of head nodes and data storage sleds, where data is replicated across multiple sleds and nodes, allowing for independent operation without relying on a zonal control plane, and utilizing redundant networks and power systems to ensure high reliability and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common control plane is used to manage data across multiple locations, then data management is simplified, but a failure of any control plane component impacts a large quantity of storage capacity and renders it unavailable
Solution Approach 1:
The control plane is segmented into multiple independent control plane nodes distributed across different locations. Each node manages a subset of storage capacity rather than a single centralized control plane managing all storage. This segmentation ensures that a failure in one control plane node only affects a portion of the total storage capacity, not the entire system.
Solution Approach 2:
Different control plane nodes are deployed in different geographic locations with locally-adapted management capabilities. Each location has its own control plane instance that can independently manage local storage resources, allowing local autonomy and reducing the impact of remote failures on local storage availability.
2Reliability
If data is stored across multiple locations to increase durability, then data redundancy is improved, but network latency for data recovery increases due to data being distributed across multiple locations
Solution Approach 1:
Data is segmented into multiple portions and distributed across different control plane nodes and storage locations. Each portion can be independently accessed and recovered, allowing parallel recovery operations that reduce overall recovery time compared to retrieving all data from a single centralized location.
Solution Approach 2:
Control plane nodes act as intermediaries between storage locations and users. When data recovery is needed, the local control plane node coordinates the retrieval process, caching frequently accessed data locally and managing the distribution of data portions across the network to minimize latency.
3Device complexity
If a server node services multiple storage nodes in a SAN architecture, then system complexity is reduced, but a failure of the server node renders large amounts of storage capacity unusable
Solution Approach 1:
The system is segmented into multiple independent control plane nodes, each capable of servicing storage nodes autonomously. This eliminates the single point of failure in traditional SAN architectures where one server node controls all storage access. Each control plane node manages a subset of storage resources independently.
Solution Approach 2:
Control plane nodes are designed to be self-sufficient, with each node capable of independently managing its assigned storage resources without requiring coordination with or dependency on other control plane nodes. This self-service capability ensures that failures in one node do not propagate to other nodes or their managed storage resources.
Data Source
AI summary
A data storage system includes multiple data storage units and a zonal control plane. The zonal control plane assigns volumes to respective ones of the data storage units. The data storage units include multiple head nodes and data storage sleds. At least one of the head nodes implements a local control plane for the data storage unit. Also, the head nodes of each data storage unit are configured to service read and write requests directed to one or more volumes serviced by the data storage unit independent of the zonal control plane.