Storage Guide

Overview

Longhorn is an open-source distributed block storage system designed specifically for Kubernetes. It provides persistent storage for stateful applications by creating and managing storage volumes that are replicated across multiple nodes to ensure high availability. Longhorn integrates seamlessly with Kubernetes, allowing users to dynamically provision, attach, and manage persistent disks through standard Kubernetes PersistentVolumeClaims (PVCs).

Longhorn deploys a set of controller and replica engines as containers on each node, forming a distributed storage system. When a volume is created, Longhorn replicates data across multiple nodes, ensuring durability even in the event of node failures. The system also handles snapshots, backups, and restores, offering robust data protection. Kubernetes automatically mounts these volumes into Pods, providing persistent storage for stateful applications to operate reliably.

graph TD
    subgraph Cluster Nodes
        Node1["Node 1"]
        Node2["Node 2"]
        Node3["Node 3"]
    end

    subgraph Longhorn Components
        Controller["Longhorn Controller"]
        Replica1["Replica (Node 1)"]
        Replica2["Replica (Node 2)"]
        Replica3["Replica (Node 3)"]
    end

    subgraph Storage Volume
        Volume["Persistent Volume"]
    end

    Node1 -->|Runs| Replica1
    Node2 -->|Runs| Replica2
    Node3 -->|Runs| Replica3

    Controller -->|Manages| Volume
    Replica1 & Replica2 & Replica3 -->|Replicate Data| Volume

Accessing the configuration GUI

Longhorn provides a web-based frontend for managing storage configurations across the Kubernetes cluster. This UI allows users to configure various aspects of the storage engine, such as the number of replicas, backup settings, snapshot management, and more.

Since this frontend does not include any authentication mechanisms and improper use could lead to significant data loss, access is restricted. To securely access the UI, a manual port-forward must be established.

You can set up a temporary connection to the Longhorn frontend using the following kubectl port-forward command:

kubectl port-forward -n longhorn-system --address 0.0.0.0 svc/longhorn-frontend 8888:80

This command forwards local port 8888 to the Longhorn frontend service in the cluster. You can then access the UI by navigating to:

http://k3s-server:8888

This connection remains active as long as the port-forward command is running. To stop it, simply press Ctrl+C. Make sure to run this command only when needed, and avoid leaving the UI accessible without proper authentication.