Clone Using YAML

Clone CSI snapshot

To clone a CSI snapshot, refer to the documentation on Creating a Volume from a Snapshot.

Clone Volume with v2 data engine

Assume you have a StorageClass named longhorn-v2:

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: longhorn-v2
provisioner: driver.longhorn.io
allowVolumeExpansion: true
reclaimPolicy: Delete
volumeBindingMode: Immediate
parameters:
  dataEngine: "v2"
  numberOfReplicas: "1"
  staleReplicaTimeout: "2880"

And you have a PersistentVolumeClaim (PVC) named source-pvc-v2 provisioned from it:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: source-pvc-v2
spec:
  storageClassName: longhorn-v2
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi

Clone using full-copy mode

You can create a new PVC with the exact same content as source-pvc-v2 by applying the YAML below. Longhorn will copy the data from the source PVC to the new PVC.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: cloned-pvc-v2
spec:
  storageClassName: longhorn-v2
  dataSource:
    name: source-pvc-v2
    kind: PersistentVolumeClaim
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi

Clone using linked-clone mode

The full-copy mode creates a new PVC that is fully independent of the source PVC. However, it requires time and resources to copy the data. Sometimes, you need to quickly create a temporary PVC with the same content as the source, without copying the data. For example, backup solutions like Velero or Kasten can use this feature to quickly create a temporary PVC to read data and upload it to an S3 bucket. In this scenario, you can use the linked-clone mode. This mode creates a new PVC that shares the same data blocks as the source PVC. Follow the steps below:

1. Create a StorageClass with cloneMode set to linked-clone.:

   kind: StorageClass
   apiVersion: storage.k8s.io/v1
   metadata:
     name: longhorn-v2-linked-clone
   provisioner: driver.longhorn.io
   reclaimPolicy: Delete
   volumeBindingMode: Immediate
   parameters:
     dataEngine: "v2"
     cloneMode: "linked-clone"
     numberOfReplicas: "1"
     staleReplicaTimeout: "2880"
   

2. Create a new PVC that uses the above StorageClass and references the source PVC in the dataSource field:

   apiVersion: v1
   kind: PersistentVolumeClaim
   metadata:
     name: cloned-pvc-v2-linked-clone
   spec:
     storageClassName: longhorn-v2-linked-clone
     dataSource:
       name: source-pvc-v2
       kind: PersistentVolumeClaim
     accessModes:
       - ReadWriteOnce
     resources:
       requests:
         storage: 10Gi
   

Note:

1. In addition to the requirements for CSI Volume Cloning, the cloned PVC’s (cloned-pvc) resources.requests.storage must match the source PVC’s (source-pvc) storage size.
2. The linked-clone mode is only supported by the v2 data engine.
3. A PVC created using linked-clone shares data blocks with the source and has the following limitations:
   • It can have only one replica.
   • It cannot be snapshotted or backed up.
   • It cannot be used as the source for another clone operation.
   • A source PVC can only have one linked-clone PVC at a time.
   • linked-clone PVCs are designed to be short-lived. It is highly recommended to delete them when no longer needed.

For more examples of linked-clone, see the blog post, Backup Applications with Longhorn V2 Volumes using Velero.

Clone Volume Using the Longhorn UI

You can also clone a v2 data engine volume using the Longhorn UI by one of the following methods:

1. On the Volumes page, click Create Volume and select the data source (Volume or Volume Snapshot).
2. From the Volumes page, select a volume and click Clone Volume in the Operation menu.
3. On the Volumes page, select a volume, click its name, and in the Snapshot and Backups section of the details page, identify the snapshot to use and then click Clone Volume.
4. For bulk cloning, on the Volumes page, select one or more volumes and click the Clone Volume button at the top of the table.

History

• GitHub Issue
• Longhorn Enhancement Proposal

Available since v1.10.0