Clone

Prerequisites

For clone, we need to have VolumeSnapshotDataSource support, which is in beta in Kubernetes 1.23. If you are using the Kubernetes version less than 1.23, you have to enable the VolumeSnapshotDataSource feature gate at kubelet and kube-apiserver.

Create Clone from Snapshot

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

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, 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.

Create Clone from Volume

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

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, 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 Local PV ZFS 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.

note

This resource has Snapname field which tells that this volume is created from that internal snapshot.