Chapter 4. Using Container Storage Interface (CSI)

1. Create a file with the VolumeSnapshotClass object described by the following YAML:

   volumesnapshotclass.yaml

   apiVersion: snapshot.storage.k8s.io
   kind: VolumeSnapshotClass 1
   metadata:
     name: csi-hostpath-snap
   driver: hostpath.csi.k8s.io
   deletionPolicy: Delete

   1

   Allows you to specify different attributes belonging to a volume snapshot.

2. Create the object you saved in the previous step by entering the following command:

   $ oc create -f volumesnapshotclass.yaml

3. Create a VolumeSnapshot object:

   volumesnapshot-dynamic.yaml

   apiVersion: snapshot.storage.k8s.io
   kind: VolumeSnapshot
   metadata:
     name: mysnap
   spec:
     volumeSnapshotClassName: csi-hostpath-snap 1
     source:
       persistentVolumeClaimName: myclaim 2

   1

   The request for a particular class by the volume snapshot. If volumeSnapshotClassName is empty, then no snapshot is created.

   2

   The name of the PersistentVolumeClaim object bound to a persistent volume. This defines what you want to create a snapshot of. Required for dynamically provisioning a snapshot.

4. Create the object you saved in the previous step by entering the following command:

   $ oc create -f volumesnapshot-dynamic.yaml

1. Provide a value for the volumeSnapshotContentName parameter as the source for the snapshot, in addition to defining volume snapshot class as shown above.

   volumesnapshot-manual.yaml

   apiVersion: snapshot.storage.k8s.io
   kind: VolumeSnapshot
   metadata:
     name: snapshot-demo
   spec:
     source:
       volumeSnapshotContentName: mycontent 1

   1

   The volumeSnapshotContentName parameter is required for pre-provisioned snapshots.

2. Create the object you saved in the previous step by entering the following command:

   $ oc create -f volumesnapshot-manual.yaml

1. To display details about the volume snapshot that was created, enter the following command:

   $ oc describe volumesnapshot mysnap

   The following example displays details about the mysnap volume snapshot:

   volumesnapshot.yaml

   apiVersion: snapshot.storage.k8s.io
   kind: VolumeSnapshot
   metadata:
     name: mysnap
   spec:
     source:
       persistentVolumeClaimName: myclaim
     volumeSnapshotClassName: csi-hostpath-snap
   status:
     boundVolumeSnapshotContentName: snapcontent-1af4989e-a365-4286-96f8-d5dcd65d78d6 1
     creationTime: "2020-01-29T12:24:30Z" 2
     readyToUse: true 3
     restoreSize: 500Mi

   1

   The pointer to the actual storage content that was created by the controller.

   2

   The time when the snapshot was created. The snapshot contains the volume content that was available at this indicated time.

   3

   If the value is set to true, the snapshot can be used to restore as a new PVC.
   If the value is set to false, the snapshot was created. However, the storage back end needs to perform additional tasks to make the snapshot usable so that it can be restored as a new volume. For example, Amazon Elastic Block Store data might be moved to a different, less expensive location, which can take several minutes.

2. To verify that the volume snapshot was created, enter the following command:

   $ oc get volumesnapshotcontent

   The pointer to the actual content is displayed. If the boundVolumeSnapshotContentName field is populated, a VolumeSnapshotContent object exists and the snapshot was created.

3. To verify that the snapshot is ready, confirm that the VolumeSnapshot object has readyToUse: true.

1. Specify the deletion policy that you require in the VolumeSnapshotClass object, as shown in the following example:

   volumesnapshot.yaml

   apiVersion: snapshot.storage.k8s.io
   kind: VolumeSnapshotClass
   metadata:
     name: csi-hostpath-snap
   driver: hostpath.csi.k8s.io
   deletionPolicy: Delete 1

   1

   If the Delete value is set, the underlying snapshot will be deleted, along with the VolumeSnapshotContent object. If the Retain value is set, both the underlying snapshot and VolumeSnapshotContent object remain.
   If the Retain value is set, and the VolumeSnapshot object is deleted without deleting the corresponding VolumeSnapshotContent object, then the content will remain. The snapshot itself is also retained in the storage back end.

Procedure

1. Specify a VolumeSnapshot data source on a PVC as shown in the following:

   pvc-restore.yaml

   apiVersion: v1
   kind: PersistentVolumeClaim
   metadata:
     name: myclaim-restore
   spec:
     storageClassName: csi-hostpath-sc
     dataSource:
       name: mysnap 1
       kind: VolumeSnapshot 2
       apiGroup: snapshot.storage.k8s.io 3
     accessModes:
       - ReadWriteOnce
     resources:
       requests:
         storage: 1Gi

   1

   Name of the VolumeSnapshot object representing the snapshot to use as source.

   2

   Must be set to the VolumeSnapshot value.

   3

   Must be set to the snapshot.storage.k8s.io value.

2. Create a PVC by entering the following command:

   $ oc create -f pvc-restore.yaml

3. Verify that the restored PVC has been created by entering the following command:

   $ oc get pvc

   Two different PVCs are displayed.

1. Create and save a file with the PersistentVolumeClaim object described by the following YAML:

   pvc-clone.yaml

   apiVersion: v1
   kind: PersistentVolumeClaim
   metadata:
     name: pvc-1-clone
     namespace: mynamespace
   spec:
     storageClassName: csi-cloning 1
     accessModes:
       - ReadWriteOnce
     resources:
       requests:
         storage: 5Gi
     dataSource:
       kind: PersistentVolumeClaim
       name: pvc-1

   1

   The name of the storage class that provisions the storage back end. The default storage class can be used and storageClassName can be omitted in the spec.

2. Create the object you saved in the previous step by running the following command:

   $ oc create -f pvc-clone.yaml

   A new PVC pvc-1-clone is created.

3. Verify that the volume clone was created and is ready by running the following command:

   $ oc get pvc pvc-1-clone

   The pvc-1-clone shows that it is Bound.

   You are now ready to use the newly cloned PVC to configure a pod.

4. Create and save a file with the Pod object described by the YAML. For example:

   kind: Pod
   apiVersion: v1
   metadata:
     name: mypod
   spec:
     containers:
       - name: myfrontend
         image: dockerfile/nginx
         volumeMounts:
         - mountPath: "/var/www/html"
           name: mypd
     volumes:
       - name: mypd
         persistentVolumeClaim:
           claimName: pvc-1-clone 1

   1

   The cloned PVC created during the CSI volume cloning operation.

   The created Pod object is now ready to consume, clone, snapshot, or delete your cloned PVC independently of its original dataSource PVC.