Longhorn is a distributed block storage system for Kubernetes.
Longhorn is lightweight, reliable, and powerful. You can install Longhorn on an existing Kubernetes cluster with one kubectl apply command or using Helm charts. Once Longhorn is installed, it adds persistent volume support to the Kubernetes cluster.
Longhorn implements distributed block storage using containers and microservices. Longhorn creates a dedicated storage controller for each block device volume and synchronously replicates the volume across multiple replicas stored on multiple nodes. The storage controller and replicas are themselves orchestrated using Kubernetes. Here are some notable features of Longhorn:
- Enterprise-grade distributed storage with no single point of failure
- Incremental snapshot of block storage
- Backup to secondary storage (NFS or S3-compatible object storage) built on efficient change block detection
- Recurring snapshot and backup
- Automated non-disruptive upgrade. You can upgrade the entire Longhorn software stack without disrupting running volumes!
- Intuitive GUI dashboard
You can read more technical details of Longhorn here.
Longhorn is alpha-quality software. We appreciate your willingness to deploy Longhorn and provide feedback.
The latest release of Longhorn is v0.4.1.
Longhorn is 100% open source software. Project source code is spread across a number of repos:
- Longhorn engine -- Core controller/replica logic https://github.com/rancher/longhorn-engine
- Longhorn manager -- Longhorn orchestration, includes Flexvolume driver for Kubernetes https://github.com/rancher/longhorn-manager
- Longhorn UI -- Dashboard https://github.com/rancher/longhorn-ui
- Docker v1.13+
- Kubernetes v1.8+. Recommend v1.12+.
open-iscsihas been installed on all the nodes of the Kubernetes cluster.- For GKE, recommended Ubuntu as guest OS image since it contains open-iscsi already.
- For Debian/Ubuntu, use
apt-get install open-iscsito install. - For RHEL/CentOS, use
yum install iscsi-initiator-utilsto install.
The easiest way to install Longhorn is to deploy Longhorn from Rancher Catalog.
- On Rancher UI, select the cluster and project you want to install Longhorn. We recommended to create a new project e.g.
Storagefor Longhorn. - Navigate to the
Catalog Appsscreen. SelectLaunch, find Longhorn in the list. SelectView Details, then clickLaunch. Longhorn will be installed in thelonghorn-systemnamespace.
After Longhorn has been successfully installed, you can access the Longhorn UI by navigating to the Catalog Apps screen.
One benefit of installing Longhorn through Rancher catalog is Rancher provides authentication to Longhorn UI.
If there is a new version of Longhorn available, you will see an Upgrade Available sign on the Catalog Apps screen. You can click Upgrade button to upgrade Longhorn manager. See more about upgrade here.
You can install Longhorn on any Kubernetes cluster using following command:
kubectl apply -f https://raw.githubusercontent.com/rancher/longhorn/master/deploy/longhorn.yaml
Google Kubernetes Engine (GKE) requires additional setup in order for Longhorn to function properly. If your are a GKE user, read this page before proceeding.
Longhorn will be installed in the namespace longhorn-system
One of the two available drivers (CSI and Flexvolume) would be chosen automatically based on the version of Kubernetes you use. See here for details.
A successful CSI-based deployment looks like this:
# kubectl -n longhorn-system get pod
NAME READY STATUS RESTARTS AGE
csi-attacher-0 1/1 Running 0 6h
csi-provisioner-0 1/1 Running 0 6h
engine-image-ei-57b85e25-8v65d 1/1 Running 0 7d
engine-image-ei-57b85e25-gjjs6 1/1 Running 0 7d
engine-image-ei-57b85e25-t2787 1/1 Running 0 7d
longhorn-csi-plugin-4cpk2 2/2 Running 0 6h
longhorn-csi-plugin-ll6mq 2/2 Running 0 6h
longhorn-csi-plugin-smlsh 2/2 Running 0 6h
longhorn-driver-deployer-7b5bdcccc8-fbncl 1/1 Running 0 6h
longhorn-manager-7x8x8 1/1 Running 0 6h
longhorn-manager-8kqf4 1/1 Running 0 6h
longhorn-manager-kln4h 1/1 Running 0 6h
longhorn-ui-f849dcd85-cgkgg 1/1 Running 0 5d
You can run kubectl -n longhorn-system get svc to get the external service IP for UI:
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
longhorn-backend ClusterIP 10.20.248.250 <none> 9500/TCP 58m
longhorn-frontend LoadBalancer 10.20.245.110 100.200.200.123 80:30697/TCP 58m
If the Kubernetes Cluster supports creating LoadBalancer, you can use EXTERNAL-IP(100.200.200.123 in the case above) of longhorn-frontend to access the Longhorn UI. Otherwise you can use <node_ip>:<port> (port is 30697in the case above) to access the UI.
Noted that the UI is unauthenticated when you installed Longhorn using YAML file.
Since v0.3.3, Longhorn is able to perform fully-automated non-disruptive upgrades, meaning that the upgrade process won't disrupt the running volumes. Existing volumes continue to run even as the software that implements these volumes are upgraded.
If you're upgrading from Longhorn v0.3.0 or newer:
- Follow the same steps for installation to upgrade Longhorn manager
- After upgraded manager, follow the steps here to upgrade Longhorn engine for existing volumes.
- For non distruptive upgrade, follow the live upgrade steps here
For more details about upgrade in Longhorn or upgrade from older versions, see here.
Before you create Kubernetes volumes, you must first create a storage class. Use following command to create a StorageClass called longhorn.
kubectl create -f https://raw.githubusercontent.com/rancher/longhorn/master/examples/storageclass.yaml
Now you can create a pod using Longhorn like this:
kubectl create -f https://raw.githubusercontent.com/rancher/longhorn/master/examples/pvc.yaml
The above yaml file contains two parts:
- Create a PVC using Longhorn StorageClass.
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: longhorn-volv-pvc
spec:
accessModes:
- ReadWriteOnce
storageClassName: longhorn
resources:
requests:
storage: 2Gi
- Use it in the a Pod as a persistent volume:
apiVersion: v1
kind: Pod
metadata:
name: volume-test
namespace: default
spec:
containers:
- name: volume-test
image: nginx:stable-alpine
imagePullPolicy: IfNotPresent
volumeMounts:
- name: volv
mountPath: /data
ports:
- containerPort: 80
volumes:
- name: volv
persistentVolumeClaim:
claimName: longhorn-volv-pvc
More examples are available at ./examples/
You can click Generate Support Bundle link at the bottom of the UI to download a zip file contains Longhorn related configuration and logs.
See here for the troubleshooting guide.
-
To prevent damaging the Kubernetes cluster, we recommend deleting all Kubernetes workloads using Longhorn volumes (PersistentVolume, PersistentVolumeClaim, StorageClass, Deployment, StatefulSet, DaemonSet, etc) first.
-
Create the uninstallation job to clean up CRDs from the system and wait for success:
kubectl create -f https://raw.githubusercontent.com/rancher/longhorn/master/uninstall/uninstall.yaml
kubectl -n longhorn-system get job/longhorn-uninstall -w
Example output:
$ kubectl create -f https://raw.githubusercontent.com/rancher/longhorn/master/uninstall/uninstall.yaml
job.batch/longhorn-uninstall created
$ kubectl -n longhorn-system get job/longhorn-uninstall -w
NAME DESIRED SUCCESSFUL AGE
longhorn-uninstall 1 0 3s
longhorn-uninstall 1 1 45s
^C
- Remove remaining components:
kubectl delete -f https://raw.githubusercontent.com/rancher/longhorn/master/deploy/longhorn.yaml
Copyright (c) 2014-2019 Rancher Labs, Inc.
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
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