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Work with snapshots

Contributors juliantap
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Beginning with the 20.01 release of Astra Trident, you can create snapshots of PVs at the Kubernetes layer. You can use these snapshots to maintain point-in-time copies of volumes that have been created by Astra Trident and schedule the creation of additional volumes (clones). Volume snapshot is supported by the ontap-nas, ontap-san, ontap-san-economy, solidfire-san, gcp-cvs, and azure-netapp-files drivers.

Note This feature is available from Kubernetes 1.17 (beta) and is GA from 1.20. To understand the changes involved in moving from beta to GA, see the release blog. With the graduation to GA, the v1 API version is introduced and is backward compatible with v1beta1 snapshots.
What you'll need

  • Creating volume snapshots requires an external snapshot controller to be created as well as some Custom Resource Definitions (CRDs). This is the responsibility of the Kubernetes orchestrator that is being used (for example: Kubeadm, GKE, OpenShift).

You can create an external snapshot-controller and snapshot CRDs as follows:

  1. 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-3.0/client/config/crd/snapshot.storage.k8s.io_volumesnapshotclasses.yaml
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/external-snapshotter/release-3.0/client/config/crd/snapshot.storage.k8s.io_volumesnapshotcontents.yaml
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/external-snapshotter/release-3.0/client/config/crd/snapshot.storage.k8s.io_volumesnapshots.yaml

  2. Create the snapshot-controller in the desired namespace. Edit the YAML manifests below to modify namespace.

    Note Don’t create a snapshot-controller if setting up on-demand volume snapshots in a GKE environment. GKE uses a built-in, hidden snapshot-controller. 
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/external-snapshotter/release-3.0/deploy/kubernetes/snapshot-controller/rbac-snapshot-controller.yaml
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/external-snapshotter/release-3.0/deploy/kubernetes/snapshot-controller/setup-snapshot-controller.yaml
Tip CSI Snapshotter provides a validating webhook to help users validate existing v1beta1 snapshots and confirm they are valid resource objects. The validating webhook automatically labels invalid snapshot objects and prevents the creation of future invalid objects. The validating webhook is deployed by the Kubernetes orchestrator. See the instructions to deploy the validating webhook manually here. Find examples of invalid snapshot manifests here.

The example detailed below explains the constructs required for working with snapshots and shows how snapshots can be created and used.

Step 1: Set up a VolumeSnapshotClass

Before creating a volume snapshot, set up a VolumeSnapshotClass.

$ cat snap-sc.yaml
#Use apiVersion v1 for Kubernetes 1.20 and above. For Kubernetes 1.17 - 1.19, use apiVersion v1beta1.
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshotClass
metadata:
  name: csi-snapclass
driver: csi.trident.netapp.io
deletionPolicy: Delete

The driver points to Astra Trident’s 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.

Step 2: Create a snapshot of an existing PVC

$ cat snap.yaml
#Use apiVersion v1 for Kubernetes 1.20 and above. For Kubernetes 1.17 - 1.19, use apiVersion v1beta1.
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
  name: pvc1-snap
spec:
  volumeSnapshotClassName: csi-snapclass
  source:
    persistentVolumeClaimName: pvc1

The snapshot is being 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

See the following example for creating 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.

Note When deleting a Persistent Volume with associated snapshots, the corresponding Trident volume is updated to a “Deleting state”. For the Astra Trident volume to be deleted, the snapshots of the volume should be removed.

Find more information