Work with snapshots

07/26/2023 Contributors

You can create Kubernetes VolumeSnapshots (volume snapshot) of Persistent Volumes (PVs) to maintain point-in-time copies of Astra Trident volumes. Additionally, you can create a new volume, also known as a clone, from an existing volume snapshot. Volume snapshot is supported by ontap-nas, ontap-nas-flexgroup, ontap-san, ontap-san-economy, solidfire-san, gcp-cvs, and azure-netapp-files drivers.

Before you begin

You must have an external snapshot controller and Custom Resource Definitions (CRDs). This is the responsibility of the Kubernetes orchestrator (for example: Kubeadm, GKE, OpenShift).

If your Kubernetes distribution does not include the snapshot controller and CRDs, refer to Deploying a volume snapshot controller.

Don't create a snapshot controller if creating on-demand volume snapshots in a GKE environment. GKE uses a built-in, hidden snapshot controller.

Step 1: Create a `VolumeSnapshotClass`

This example creates a volume snapshot class.

cat snap-sc.yaml
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshotClass
metadata:
  name: csi-snapclass
driver: csi.trident.netapp.io
deletionPolicy: Delete

The driver points to the Astra Trident CSI driver. deletionPolicy can be Delete or Retain. When set to Retain, the underlying physical snapshot on the storage cluster is retained even when the VolumeSnapshot object is deleted.

For more information, refer to VolumeSnapshotClass.

Step 2: Create a snapshot of an existing PVC

This example creates a snapshot of an existing PVC.

cat snap.yaml
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
  name: pvc1-snap
spec:
  volumeSnapshotClassName: csi-snapclass
  source:
    persistentVolumeClaimName: pvc1

In this example, the snapshot is created for a PVC named pvc1 and the name of the snapshot is set to pvc1-snap.

kubectl create -f snap.yaml
volumesnapshot.snapshot.storage.k8s.io/pvc1-snap created

kubectl get volumesnapshots
NAME                   AGE
pvc1-snap              50s

This created a VolumeSnapshot object. A VolumeSnapshot is analogous to a PVC and is associated with a VolumeSnapshotContent object that represents the actual snapshot.

It is possible to identify the VolumeSnapshotContent object for the pvc1-snap VolumeSnapshot by describing it.

kubectl describe volumesnapshots pvc1-snap
Name:         pvc1-snap
Namespace:    default
.
.
.
Spec:
  Snapshot Class Name:    pvc1-snap
  Snapshot Content Name:  snapcontent-e8d8a0ca-9826-11e9-9807-525400f3f660
  Source:
    API Group:
    Kind:       PersistentVolumeClaim
    Name:       pvc1
Status:
  Creation Time:  2019-06-26T15:27:29Z
  Ready To Use:   true
  Restore Size:   3Gi
.
.

The Snapshot Content Name identifies the VolumeSnapshotContent object which serves this snapshot. The Ready To Use parameter indicates that the Snapshot can be used to create a new PVC.

Step 3: Create PVCs from VolumeSnapshots

This example creates a PVC using a snapshot.

cat pvc-from-snap.yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc-from-snap
spec:
  accessModes:
    - ReadWriteOnce
  storageClassName: golden
  resources:
    requests:
      storage: 3Gi
  dataSource:
    name: pvc1-snap
    kind: VolumeSnapshot
    apiGroup: snapshot.storage.k8s.io

dataSource shows that the PVC must be created using a VolumeSnapshot named pvc1-snap as the source of the data. This instructs Astra Trident to create a PVC from the snapshot. After the PVC is created, it can be attached to a pod and used just like any other PVC.

The PVC must be created in the same namespace as its dataSource.

Deleting a PV with snapshots

When deleting a Persistent Volume with associated snapshots, the corresponding Trident volume is updated to a “Deleting state”. Remove the volume snapshots to delete the Astra Trident volume.

Deploying a volume snapshot controller

If your Kubernetes distribution does not include the snapshot controller and CRDs, you can deploy them as follows.

Steps

Create volume snapshot CRDs.

cat snapshot-setup.sh
#!/bin/bash
# Create volume snapshot CRDs
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/external-snapshotter/release-6.1/client/config/crd/snapshot.storage.k8s.io_volumesnapshotclasses.yaml
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/external-snapshotter/release-6.1/client/config/crd/snapshot.storage.k8s.io_volumesnapshotcontents.yaml
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/external-snapshotter/release-6.1/client/config/crd/snapshot.storage.k8s.io_volumesnapshots.yaml

Create the snapshot controller.

kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/external-snapshotter/release-6.1/deploy/kubernetes/snapshot-controller/rbac-snapshot-controller.yaml
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/external-snapshotter/release-6.1/deploy/kubernetes/snapshot-controller/setup-snapshot-controller.yaml

If necessary, open deploy/kubernetes/snapshot-controller/rbac-snapshot-controller.yaml and update namespace to your namespace.

Recover volume data using snapshots

The snapshot directory is hidden by default to facilitate maximum compatibility of volumes provisioned using the ontap-nas and ontap-nas-economy drivers. Enable the .snapshot directory to recover data from snapshots directly.

Use the volume snapshot restore ONTAP CLI to to restore a volume to a state recorded in a prior snapshot.

cluster1::*> volume snapshot restore -vserver vs0 -volume vol3 -snapshot vol3_snap_archive

When you restore a snapshot copy, the existing volume configuration is overwritten. Changes made to volume data after the snapshot copy was created are lost.