Snapshots of persistent volumes in a Managed Kubernetes cluster

VolumeSnapshots are copies of the contents of PersistentVolumes in a Managed Kubernetes cluster at a particular point in time.

Snapshots can be used to back up data or move data to another share without having to create a new disk.

In Managed Kubernetes, snapshots run on cloud platform resources.

Create a snapshot

Configure the Volume Snapshot Controller, one of the components of CSI Snapshotter:

kubectl apply -f https://raw.githubusercontent.com/selectel/mks-csi-snapshotter/master/deploy/setup-snapshot-controller.yaml

The response will list the objects created. For example:

deployment.apps/snapshot-controller created
serviceaccount/snapshot-controller created
clusterrole.rbac.authorization.k8s.io/snapshot-controller-runner created
clusterrolebinding.rbac.authorization.k8s.io/snapshot-controller-role created
role.rbac.authorization.k8s.io/snapshot-controller-leaderelection created
rolebinding.rbac.authorization.k8s.io/snapshot-controller-leaderelection created
customresourcedefinition.apiextensions.k8s.io/volumesnapshots.snapshot.storage.k8s.io created
customresourcedefinition.apiextensions.k8s.io/volumesnapshotcontents.snapshot.storage.k8s.io created
customresourcedefinition.apiextensions.k8s.io/volumesnapshotclasses.snapshot.storage.k8s.io created

Make sure that pods with Volume Snapshot Controller are created:

kubectl get pod -l app=snapshot-controller --namespace=kube-system

A list of pods will appear in the response. For example:

NAME                                   READY   STATUS    RESTARTS   AGE
snapshot-controller-7d7f5775d4-cz9j4   1/1     Running   0          3m37s
snapshot-controller-7d7f5775d4-tc42c   1/1     Running   0          3m37s

Create a yaml file with a manifest for the VolumeSnapshotClass and VolumeSnapshot objects:

Manifesto example:

---
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshotClass
metadata:
name: csi-hostpath-snapclass-v1
driver: cinder.csi.openstack.org
deletionPolicy: Delete
parameters:
force-create: "true"
---
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
name: new-snapshot-demo
spec:
volumeSnapshotClassName: csi-hostpath-snapclass-v1
source:
    persistentVolumeClaimName: my-pv-claim

Here:

csi-hostpath-snapclass-v1 - name of the SnapshotClass object;
new-snapshot-demo - name of the VolumeSnapshot object;
my-pv-claim - the name of the PersistentVolumeClaim object whose snapshot you are creating.

Apply the manifest:
```
kubectl apply -f <file_name>
```
Specify <file_name> - the name of the yaml file with the manifest for VolumeSnapshotClass and VolumeSnapshot objects. For example, snapshot.yaml.

The response will show a message that the objects have been created. For example:
```
volumesnapshotclass.snapshot.storage.k8s.io/csi-hostpath-snapclass-v1 created
volumesnapshot.snapshot.storage.k8s.io/new-snapshot-demo created
```

Make sure that a VolumeSnapshotContent object is created:

kubectl get volumesnapshotcontents.snapshot.storage.k8s.io

The created VolumeSnapshotContent object will appear in the response. For example:

NAME                                               READYTOUSE   RESTORESIZE   DELETIONPOLICY   DRIVER                     VOLUMESNAPSHOTCLASS         VOLUMESNAPSHOT      VOLUMESNAPSHOTNAMESPACE   AGE
snapcontent-acc83be5-065f-42c1-a465-9f26497de1b1                              Delete           cinder.csi.openstack.org   csi-hostpath-snapclass-v1   new-snapshot-demo   default                   9m7s

Restore a persistent volume from a snapshot

Create a yaml file with a manifest to create a new PersistentVolumeClaim from the snapshot.

Manifesto example:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: snapshot-demo-restore
spec:
storageClassName: fast.ru-3b
dataSource:
    name: new-snapshot-demo
    kind: VolumeSnapshot
    apiGroup: snapshot.storage.k8s.io
accessModes:
    - ReadWriteOnce
resources:
    requests:
    storage: 10Gi

Here:

snapshot-demo-restore - the name of a new PersistentVolumeClaim object to which the snapshot data will be copied;
new-snapshot-demo - name of the snapshot from which you will restore the object.

Apply the manifest:
```
kubectl apply -f <file_name>
```
Specify <file_name> is the name of the yaml file with the manifest to create a new PersistentVolumeClaim from the snapshot. For example, snapshot-restore.yaml.

Ensure that a new PersistentVolumeClaim object is created:

kubectl get pvc

A new PersistentVolumeClaim will appear in the response. For example:

NAME          STATUS   VOLUME     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
snapshot-demo-restore   Bound    pvc-62394055-3780-4324-8871-1a56a447d70f   10Gi       RWO            fast.ru-3b     22m