Restoring Volumes for Kubernetes StatefulSets
Longhorn supports restoring backups, and one of the use cases for this feature is to restore data for use in a Kubernetes StatefulSet, which requires restoring a volume for each replica that was backed up.
To restore, follow the below instructions. The example below uses a StatefulSet with one volume attached to each Pod and two replicas.
Connect to the Longhorn UI
page in your web browser. Under the Backup
tab, select the name of the StatefulSet volume. Click the dropdown menu of the volume entry and restore it. Name the volume something that can easily be referenced later for the Persistent Volumes
.
pvc-01a
and pvc-02b
, the restore could look like this:Backup Name | Restored Volume |
---|---|
pvc-01a | statefulset-vol-0 |
pvc-02b | statefulset-vol-1 |
In Kubernetes, create a Persistent Volume
for each Longhorn volume that was created. Name the volumes something that can easily be referenced later for the Persistent Volume Claims
. storage
capacity, numberOfReplicas
, storageClassName
, and volumeHandle
must be replaced below. In the example, we’re referencing statefulset-vol-0
and statefulset-vol-1
in Longhorn and using longhorn
as our storageClassName
.
apiVersion: v1
kind: PersistentVolume
metadata:
name: statefulset-vol-0
spec:
capacity:
storage: <size> # must match size of Longhorn volume
volumeMode: Filesystem
accessModes:
- ReadWriteOnce
persistentVolumeReclaimPolicy: Delete
csi:
driver: driver.longhorn.io # driver must match this
fsType: ext4
volumeAttributes:
numberOfReplicas: <replicas> # must match Longhorn volume value
staleReplicaTimeout: '30' # in minutes
volumeHandle: statefulset-vol-0 # must match volume name from Longhorn
storageClassName: longhorn # must be same name that we will use later
---
apiVersion: v1
kind: PersistentVolume
metadata:
name: statefulset-vol-1
spec:
capacity:
storage: <size> # must match size of Longhorn volume
volumeMode: Filesystem
accessModes:
- ReadWriteOnce
persistentVolumeReclaimPolicy: Delete
csi:
driver: driver.longhorn.io # driver must match this
fsType: ext4
volumeAttributes:
numberOfReplicas: <replicas> # must match Longhorn volume value
staleReplicaTimeout: '30'
volumeHandle: statefulset-vol-1 # must match volume name from Longhorn
storageClassName: longhorn # must be same name that we will use later
2.1 In the case of encrypted volume, make sure you are specifying the
nodePublishSecretRef
, andnodeStageSecretRef
while creating thePV
.kind: PersistentVolume metadata: name: statefulset-encrypted-vol-0 spec: capacity: storage: <size> volumeMode: Filesystem accessModes: - ReadWriteOnce persistentVolumeReclaimPolicy: Delete csi: driver: driver.longhorn.io fsType: ext4 nodePublishSecretRef: name: <secret-name> namespace: <namespace> nodeStageSecretRef: name: <secret-name> namespace: <namespace> volumeAttributes: numberOfReplicas: <replicas> staleReplicaTimeout: "30" volumeHandle: statefulset-encrypted-vol-0 storageClassName: longhorn
In the namespace
the StatefulSet
will be deployed in, create PersistentVolume Claims for each Persistent Volume
. The name of the Persistent Volume Claim
must follow this naming scheme:
<name of Volume Claim Template>-<name of StatefulSet>-<index>
StatefulSet Pods are zero-indexed. In this example, the name of the Volume Claim Template
is data
, the name of the StatefulSet
is webapp
, and there
are two replicas, which are indexes 0
and 1
.
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: data-webapp-0
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 2Gi # must match size from earlier
storageClassName: longhorn # must match name from earlier
volumeName: statefulset-vol-0 # must reference Persistent Volume
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: data-webapp-1
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 2Gi # must match size from earlier
storageClassName: longhorn # must match name from earlier
volumeName: statefulset-vol-1 # must reference Persistent Volume
Create the StatefulSet
:
apiVersion: apps/v1beta2
kind: StatefulSet
metadata:
name: webapp # match this with the PersistentVolumeClaim naming scheme
spec:
selector:
matchLabels:
app: nginx # has to match .spec.template.metadata.labels
serviceName: "nginx"
replicas: 2 # by default is 1
template:
metadata:
labels:
app: nginx # has to match .spec.selector.matchLabels
spec:
terminationGracePeriodSeconds: 10
containers:
- name: nginx
image: registry.k8s.io/nginx-slim:0.8
ports:
- containerPort: 80
name: web
volumeMounts:
- name: data
mountPath: /usr/share/nginx/html
volumeClaimTemplates:
- metadata:
name: data # match this with the PersistentVolumeClaim naming scheme
spec:
accessModes: [ "ReadWriteOnce" ]
storageClassName: longhorn # must match name from earlier
resources:
requests:
storage: 2Gi # must match size from earlier
Result: The restored data should now be accessible from inside the StatefulSet
Pods
.
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