Managing Volume Snapshots in Kubernetes (CloudPE)

1. Executive Summary

Kubernetes supports volume snapshots, allowing you to capture the contents of a Persistent Volume at a specific point in time.

• Snapshots are useful for restoring volume data in case of accidental deletion, corruption, or data loss.
• Volume snapshots are implemented as Custom Resource Definitions (CRDs) and must be installed on the cluster before use.
• ✅ Creating a snapshot does not modify or move the source volume’s data.

2. Prerequisites

Before starting, ensure the following:

📦 Persistent Volume Claim

• A PersistentVolumeClaim (PVC) must already exist.
• See “Dynamically Provisioning Persistent Volumes” for details.

🚀 CSI Snapshotter Version

• The CSI snapshotter version used must not be higher than release-5.0.

🔧 Required Components

• VolumeSnapshotClass, VolumeSnapshotContent, and VolumeSnapshot CRDs
• Snapshot-controller RBAC resources (ClusterRole, ServiceAccount, ClusterRoleBinding, Role, RoleBinding)
• Snapshot-controller deployment

3. Installing the Custom Resource Definitions

This method follows Infrastructure as Code (IaC) best practices using manifests from the upstream external-snapshotter repository.

🔹 Phase A: Clone the Repository

1. Clone the external-snapshotter repository and check out the supported release:

git clone https://github.com/kubernetes-csi/external-snapshotter/
cd ./external-snapshotter
git checkout release-5.0

🔹 Phase B: Apply the CRDs

2. Apply the VolumeSnapshotClass, VolumeSnapshotContent, and VolumeSnapshot CRDs:

kubectl apply -f client/config/crd/snapshot.storage.k8s.io_volumesnapshotclasses.yaml
kubectl apply -f client/config/crd/snapshot.storage.k8s.io_volumesnapshotcontents.yaml
kubectl apply -f client/config/crd/snapshot.storage.k8s.io_volumesnapshots.yaml

🔹 Phase C: Deploy the Snapshot Controller

3. Apply the RBAC rules and the snapshot-controller deployment in the kube-system namespace:

kubectl apply -f deploy/kubernetes/snapshot-controller/rbac-snapshot-controller.yaml -n kube-system
kubectl apply -f deploy/kubernetes/snapshot-controller/setup-snapshot-controller.yaml -n kube-system

These commands create:

• CRDs for VolumeSnapshotClass, VolumeSnapshotContent, and VolumeSnapshot
• The required ClusterRole, ServiceAccount, ClusterRoleBinding, Role, and RoleBinding
• The snapshot-controller deployment

4. Creating a Volume Snapshot

🔹 Phase A: Define a VolumeSnapshotClass

1. Create a snapshot-class.yaml file:

vi snapshot-class.yaml
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshotClass
metadata:
name: mysnapclass
driver: cinder.csi.openstack.org
deletionPolicy: Delete
parameters:
force-create: "true"

• This defines the volume snapshot class mysnapclass with the deletion policy Delete.
• Delete removes the underlying storage snapshot along with the VolumeSnapshotContent object when the VolumeSnapshot is deleted.
• Set the policy to Retain instead to keep both the underlying snapshot and the VolumeSnapshotContent object after the VolumeSnapshot is deleted.

1. Apply the snapshot class:

kubectl apply -f snapshot-class.yaml

Expected output:

volumesnapshotclass.snapshot.storage.k8s.io/mysnapclass created

🔹 Phase B: Define a VolumeSnapshot

3. Create a snapshot.yaml file:

vi snapshot.yaml 
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
name: mysnapshot
spec:
volumeSnapshotClassName: mysnapclass
source:
persistentVolumeClaimName: mypvc

• This defines the volume snapshot mysnapshot, based on the mysnapclass snapshot class.
• It creates a snapshot of the volume bound to PVC mypvc.

1. Create the volume snapshot:

kubectl create -f snapshot.yaml

Expected output:

volumesnapshot.snapshot.storage.k8s.io/mysnapshot created

💡 In the self-service panel, the new snapshot appears under Compute → Volumes → [Volume] → Snapshots.

• Also you can verify the snapshots with below command

kubectl get vs

5. Deleting a Volume Snapshot

Run the following command:

kubectl delete -f snapshot.yaml

Expected output:

volumesnapshot.snapshot.storage.k8s.io "mysnapshot" deleted

⚠️ Whether the underlying storage snapshot is also removed depends on the deletionPolicy set on the associated VolumeSnapshotClass (Delete vs. Retain).

6. Safety & Recovery

🔒 Data Integrity

• Creating a snapshot does not alter, move, or delete data on the source volume.
• Snapshots capture volume state at the moment of creation and can be used to restore data later.

⚠️ Version Compatibility

• Using a CSI snapshotter version higher than release-5.0 is not supported and may cause the CRDs or snapshot-controller to behave unexpectedly.

🕒 Best Practice

• Take snapshots on a regular schedule, especially before major changes or upgrades to workloads using the volume.
• Use the Retain deletion policy for critical volumes so the underlying snapshot survives accidental deletion of the VolumeSnapshot object.

✅ Summary

• Volume snapshots let you capture PVC data at a point in time for recovery purposes.
• Requires:
• External-snapshotter CRDs and snapshot-controller (version ≤ release-5.0)
• A VolumeSnapshotClass
• A VolumeSnapshot referencing an existing PVC
• Delete snapshots with kubectl delete -f snapshot.yaml when no longer needed.