For clone, we need to have VolumeSnapshotDataSource support, which is in beta in Kubernetes 1.17. If you are using the Kubernetes version less than 1.17, you have to enable the VolumeSnapshotDataSource feature gate at kubelet and kube-apiserver.
We can create a clone volume from a snapshot and use that volume for some application. We can create a PVC YAML and mention the snapshot name in the datasource.
$ cat clone.yaml
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
name: zfspv-clone
spec:
storageClassName: openebs-zfspv
dataSource:
name: zfspv-snap
kind: VolumeSnapshot
apiGroup: snapshot.storage.k8s.io
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 4Gi
The above yaml says that create a volume from the snapshot zfspv-snap. Applying the above yaml will create a clone volume on the same node where the original volume is present. The newly created clone PV will also be there on the same node where the original PV is there. Apply the clone yaml
$ kubectl apply -f clone.yaml
persistentvolumeclaim/zfspv-clone created
Note that the clone PVC should also be of the same size as that of the original volume. Currently resize is not supported. Also, note that the poolname should also be same, as across the ZPOOL clone is not supported. So, if you are using a separate storageclass for the clone PVC, please make sure it refers to the same ZPOOL.
$ kubectl get pvc
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
csi-zfspv Bound pvc-73402f6e-d054-4ec2-95a4-eb8452724afb 4Gi RWO openebs-zfspv 13m
zfspv-clone Bound pvc-c095aa52-8d09-4bbe-ac3c-bb88a0e7be19 4Gi RWO openebs-zfspv 34s
We can see in the above output that zfspv-clone claim has been created and it is bound. Also, we can check the zfs list on node and verify that clone volume is created.
$ zfs list -t all
NAME USED AVAIL REFER MOUNTPOINT
test-pool 834K 9.63G 24K /test-pool
test-pool/pvc-73402f6e-d054-4ec2-95a4-eb8452724afb 24K 4.00G 24K /var/lib/kubelet/pods/3862895a-8a67-446e-80f7-f3c18881e391/volumes/kubernetes.io~csi/pvc-73402f6e-d054-4ec2-95a4-eb8452724afb/mount
test-pool/pvc-73402f6e-d054-4ec2-95a4-eb8452724afb@snapshot-3cbd5e59-4c6f-4bd6-95ba-7f72c9f12fcd 0B - 24K -
test-pool/pvc-c095aa52-8d09-4bbe-ac3c-bb88a0e7be19 0B 9.63G 24K none
The clone volume will have properties same as snapshot properties which are the properties when that snapshot has been created. The ZFSVolume object for the clone volume will be something like below:
$ kubectl describe zv pvc-c095aa52-8d09-4bbe-ac3c-bb88a0e7be19 -n openebs
Name: pvc-c095aa52-8d09-4bbe-ac3c-bb88a0e7be19
Namespace: openebs
Labels: kubernetes.io/nodename=e2e1-node2
Annotations: none
API Version: openebs.io/v1alpha1
Kind: ZFSVolume
Metadata:
Creation Timestamp: 2020-02-25T08:34:25Z
Finalizers:
zfs.openebs.io/finalizer
Generation: 1
Resource Version: 448930
Self Link: /apis/openebs.io/v1alpha1/namespaces/openebs/zfsvolumes/pvc-c095aa52-8d09-4bbe-ac3c-bb88a0e7be19
UID: e38a9f9a-fb76-466b-a6f9-8d070e0bec6f
Spec:
Capacity: 4294967296
Fs Type: zfs
Owner Node ID: e2e1-node2
Pool Name: test-pool
Snapname: pvc-73402f6e-d054-4ec2-95a4-eb8452724afb@snapshot-3cbd5e59-4c6f-4bd6-95ba-7f72c9f12fcd
Volume Type: DATASET
Events: none
Here you can note that this resource has Snapname field which tells that this volume is created from that snapshot.
We can create a clone volume from an existing volume and use that volume for some application. We can create a PVC YAML and mention the source volume name from where we want to create the clone in the datasource.
$ cat clone.yaml
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
name: zfspv-clone
spec:
storageClassName: openebs-zfspv
dataSource:
name: zfspv-pvc
kind: PersistentVolumeClaim
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 4Gi
The above yaml says that create a clone from the pvc zfspv-pvc as source. Applying the above yaml will create a clone volume on the same node where the original volume is present. The newly created clone PV will also be there on the same node where the original PV is there. Apply the clone yaml
$ kubectl apply -f clone.yaml
persistentvolumeclaim/zfspv-clone created
Note that the clone PVC should also be of the same size as that of the original volume. Also, note that the poolname should also be same, as across the ZPOOL clone is not supported. So, if you are using a separate storageclass for the clone PVC, please make sure it refers to the same ZPOOL.
$ kubectl get pvc
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
zfspv-clone Bound pvc-b757fbca-f008-49c6-954e-7ea3e1c1bbc7 4Gi RWO openebs-zfspv 52s
zfspv-pvc Bound pvc-9df1e7ba-bcb1-414a-b318-5084f4f6edeb 4Gi RWO openebs-zfspv 92s
We can see in the above output that zfspv-clone claim has been created and it is bound. Also, we can check the zfs list on node and verify that clone volume is created.
$ zfs list -t all
NAME USED AVAIL REFER MOUNTPOINT
zfspv-pool 4.26G 497G 24K /zfspv-pool
zfspv-pool/pvc-9df1e7ba-bcb1-414a-b318-5084f4f6edeb 4.25G 502G 130M -
zfspv-pool/pvc-9df1e7ba-bcb1-414a-b318-5084f4f6edeb@pvc-b757fbca-f008-49c6-954e-7ea3e1c1bbc7 0B - 130M -
zfspv-pool/pvc-b757fbca-f008-49c6-954e-7ea3e1c1bbc7 67K 497G 130M -
The clone volume will have properties same as source volume properties at the time of creating the clone. The ZFSVolume object for the clone volume will be something like below:
$ kubectl describe zv pvc-b757fbca-f008-49c6-954e-7ea3e1c1bbc7 -n openebs
Name: pvc-b757fbca-f008-49c6-954e-7ea3e1c1bbc7
Namespace: openebs
Labels: kubernetes.io/nodename=pawan-node-1
openebs.io/source-volume=pvc-9df1e7ba-bcb1-414a-b318-5084f4f6edeb
Annotations: <none>
API Version: zfs.openebs.io/v1
Kind: ZFSVolume
Metadata:
Creation Timestamp: 2020-12-10T05:00:54Z
Finalizers:
zfs.openebs.io/finalizer
Generation: 2
Resource Version: 53615100
Self Link: /apis/zfs.openebs.io/v1/namespaces/openebs/zfsvolumes/pvc-b757fbca-f008-49c6-954e-7ea3e1c1bbc7
UID: b67ea231-0f5c-4d15-918c-425160706953
Spec:
Capacity: 4294967296
Owner Node ID: pawan-node-1
Pool Name: zfspv-pool
Snapname: pvc-9df1e7ba-bcb1-414a-b318-5084f4f6edeb@pvc-b757fbca-f008-49c6-954e-7ea3e1c1bbc7
Volume Type: ZVOL
Status:
State: Ready
Events: <none>
The ZFS-LocalPV driver creates an internal snapshot on the source volume with the name same as clone volume name and then creates the clone from that snapshot. Here you can note that this resource has Snapname field which tells that this volume is created from that internal snapshot.