What is Longhorn?

Longhorn is a lightweight, distributed block storage system designed for Kubernetes. Created by Rancher Labs, it’s built specifically for cloud-native environments and enables highly available persistent volumes using standard Kubernetes interfaces.

Key Features

  • Cloud-native: Designed specifically for Kubernetes.
  • Highly Available: Replicates volumes across nodes.
  • UI and CLI Tools: Easily manage storage through web interface or CLI.
  • Incremental Snapshots and Backups: Built-in support.
  • Easy to Deploy and Use: Helm and YAML options available.

Why Use Longhorn?

Kubernetes does not manage storage on its own — it needs a CSI (Container Storage Interface) driver. Longhorn is a popular open-source choice that offers:

  • Minimal operational overhead
  • High availability with replication
  • Easy recovery and backup
  • Support for dynamic provisioning of volumes

How to Install Longhorn

Prerequisites

  • A running Kubernetes cluster (1.20+)
  • Helm 3 installed
  • Open TCP ports 9500, 9501, and 3260 on all nodes

Step-by-Step Installation with Helm

helm repo add longhorn https://charts.longhorn.io
helm repo update
kubectl create namespace longhorn-system
helm install longhorn longhorn/longhorn --namespace longhorn-system

Access the Longhorn UI

kubectl port-forward service/longhorn-frontend 8080:80 -n longhorn-system

Then open http://localhost:8080

How to Use Longhorn in Your Apps

  1. Create a StorageClass (optional):
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: longhorn
provisioner: driver.longhorn.io
reclaimPolicy: Retain
  1. Create a PersistentVolumeClaim:
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  accessModes:
    - ReadWriteOnce
  storageClassName: longhorn
  resources:
    requests:
      storage: 2Gi
  1. Mount in Your Deployment
volumeMounts:
  - name: data
    mountPath: /data
volumes:
  - name: data
    persistentVolumeClaim:
      claimName: my-pvc

Pros and Cons

✅ Pros

  • Easy to set up and use
  • Supports UI, CLI, and API
  • Incremental backups
  • Lightweight and open-source

❌ Cons

  • Performance can be lower than native local volumes
  • Doesn’t support all CSI features yet
  • More components = more points of failure

Conclusion

Longhorn is a powerful and easy-to-use storage solution for Kubernetes, especially for clusters that need persistent volumes with high availability. It’s ideal for DevOps teams looking for a robust, open-source alternative to complex distributed storage systems.