Name: longhorn
Owner: Rancher
Description: Distributed block storage for Kubernetes
Created: 2017-04-14 19:57:01.0
Updated: 2018-05-24 11:44:23.0
Pushed: 2018-04-14 03:05:21.0
Size: 51
Language: null
GitHub Committers
| User | Most Recent Commit | # Commits |
|---|
Other Committers
| User | Most Recent Commit | # Commits |
|---|
Longhorn is a distributed block storage system for Kubernetes. Longhorn is lightweight, reliable, and easy-to-use. You can deploy Longhorn on an existing Kubernetes cluster with one simple command. Once Longhorn is deployed, 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 sychronously replicates the volume across multiple replicas stored on multiple nodes. The storage controller and replicas are themselves orchestrated using Kubernetes. Longhorn supports snapshots, backups, and even allows you to schedule recurring snapshots and backups!
You can read more details of Longhorn and its design here.
Longhorn is a work in progress. We appreciate your comments as we continue to work on it!
Longhorn is 100% open source software. Project source code is spread across a number of repos:
curl, findmnt, grep, awk and blkid has been installed in all nodes of the Kubernetes cluster.open-iscsi has been installed in all nodes of the Kubernetes cluster. For GKE, recommended Ubuntu as guest OS image since it contains open-iscsi already.Create the deployment of Longhorn in your Kubernetes cluster is easy. For most Kubernetes setup (except GKE), you will only need to run the following command to install Longhorn:
ctl create -f https://raw.githubusercontent.com/rancher/longhorn/master/deploy/longhorn.yaml
For Google Kubernetes Engine (GKE) users, see here before proceed.
Longhorn Manager and Longhorn Driver will be deployed as daemonsets in a separate namespace called longhorn-system, as you can see in the yaml file.
When you see those pods has started correctly as follows, you've deployed the Longhorn successfully.
bectl -n longhorn-system get pod
READY STATUS RESTARTS AGE
horn-flexvolume-driver-4dnx6 1/1 Running 0 1d
horn-flexvolume-driver-cqwj5 1/1 Running 0 1d
horn-flexvolume-driver-deployer-bc7b95b5b-sb9kr 1/1 Running 0 1d
horn-flexvolume-driver-q9h4f 1/1 Running 0 1d
horn-manager-dkdn9 1/1 Running 0 2h
horn-manager-l6npd 1/1 Running 0 2h
horn-manager-v4fz8 1/1 Running 0 2h
horn-ui-58796c68d-db4t6 1/1 Running 0 1h
Use kubectl -n longhorn-system get svc to get the external service IP for UI:
TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
horn-backend ClusterIP 10.20.248.250 <none> 9500/TCP 58m
horn-frontend LoadBalancer 10.20.245.110 100.200.200.123 80:30697/TCP 58m
If the Kubernetes Cluster supports creating LoadBalancer, user can then use EXTERNAL-IP(100.200.200.123 in the case above) of longhorn-frontend to access the Longhorn UI. Otherwise the user can use <node_ip>:<port> (port is 30697 in the case above) to access the UI.
Longhorn UI would connect to the Longhorn Manager API, provides the overview of the system, the volume operations, and the snapshot/backup operations. It's highly recommended for the user to check out Longhorn UI.
Notice the current UI is unauthenticated.
There are serveral ways to use the Longhorn volume.
The following YAML file shows the definition of a pod that makes the Longhorn attach a volume to be used by the pod.
ersion: v1
: Pod
data:
me: volume-test
mespace: default
:
ntainers:
name: volume-test
image: nginx:stable-alpine
imagePullPolicy: IfNotPresent
volumeMounts:
- name: voll
mountPath: /data
ports:
- containerPort: 80
lumes:
name: voll
flexVolume:
driver: "rancher.io/longhorn"
fsType: "ext4"
options:
size: "2Gi"
numberOfReplicas: "3"
staleReplicaTimeout: "20"
fromBackup: ""
Notice this field in YAML file flexVolume.driver "rancher.io/longhorn". It specifies Longhorn FlexVolume plug-in shoule be used. There are some options fields in options user can fill.
Option | Required | Description
————- | —-|———
size | Yes | Specify the capacity of the volume in longhorn and the unit should be G
numberOfReplicas | Yes | The number of replica (HA feature) for volume in this Longhorn volume
fromBackup | No | Optional. Must be a Longhorn Backup URL. Specify where user want to restore the volume from.
Longhorn supports dynamic provisioner function, which can create PV automatically for the user according to the spec of storage class and PVC. User need to create a new storage class in order to use it. The storage class example is at here
: StorageClass
ersion: storage.k8s.io/v1
data:
me: longhorn
isioner: rancher.io/longhorn
meters:
mberOfReplicas: "3"
aleReplicaTimeout: "30"
omBackup: ""
Then user can create PVC directly. For example:
ersion: v1
: PersistentVolumeClaim
data:
me: longhorn-volv-pvc
:
cessModes:
- ReadWriteOnce
orageClassName: longhorn
sources:
requests:
storage: 2Gi
THen use it in the pod:
ersion: v1
: Pod
data:
me: volume-test
mespace: default
:
ntainers:
name: volume-test
image: nginx:stable-alpine
imagePullPolicy: IfNotPresent
volumeMounts:
- name: volv
mountPath: /data
ports:
- containerPort: 80
lumes:
name: volv
persistentVolumeClaim:
claimName: longhorn-volv-pvc
Longhorn supports backing up mechanism to export the user data out of Longhorn system. Currently Longhorn supports backing up to a NFS server. In order to use this feature, you need to have a NFS server running and accessible in the Kubernetes cluster. Here we provides a simple way help to setup a testing NFS server.
WARNING: This NFS server won't save any data after you delete it. It's for TESTING ONLY.
ctl create -f deploy/example-backupstore.yaml
It will create a simple NFS server in the default namespace, which can be addressed as longhorn-test-nfs-svc.default for other pods in the cluster.
After this script completes, using the following URL as the Backup Target in the Longhorn setting:
//longhorn-test-nfs-svc.default:/opt/backupstore
Open Longhorn UI, go to Setting, fill the Backup Target field with the URL above, click Save. Now you should able to use the backup feature of Longhorn.
The configuration yaml will be slight different for Google Kubernetes Engine (GKE):
GKE requires user to manually claim himself as cluster admin to enable RBAC. User need to execute following command before create the Longhorn system using yaml files.
ctl create clusterrolebinding cluster-admin-binding --clusterrole=cluster-admin --user=<name@example.com>
In which name@example.com is the user's account name in GCE, and it's case sensitive.
See here for details.
The default Flexvolume plugin directory is different with GKE 1.8+, which is at /home/kubernetes/flexvolume. User need to use following command instead:
ctl create -f https://raw.githubusercontent.com/rancher/longhorn/master/deploy/longhorn-gke.yaml
User can also customerize the Flexvolume directory in the last part of the Longhorn system deployment yaml file, e.g.:
- name: FLEXVOLUME_DIR
value: "/home/kubernetes/flexvolume/"
See Troubleshooting for details.
In order to uninstall Longhorn, user need to remove all the volumes first:
ctl -n longhorn-system delete lhv --all
After confirming all the volumes are removed, then Longhorn can be easily uninstalled using:
ctl delete -f https://raw.githubusercontent.com/rancher/longhorn/master/deploy/longhorn.yaml
Check if volume plugin directory has been set correctly.
By default, Kubernetes use /usr/libexec/kubernetes/kubelet-plugins/volume/exec/ as the directory for volume plugin drivers, as stated in the official document.
But some vendors may choose to change the directory due to various reasons. For example, GKE uses /home/kubernetes/flexvolume instead.
User can find the correct directory by running ps aux|grep kubelet on the host and check the --volume-plugin-dir parameter. If there is none, the default /usr/libexec/kubernetes/kubelet-plugins/volume/exec/ will be used.
Copyright (c) 2014-2018 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
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.