CSI VolumeSnapshot Associated with Longhorn Snapshot
Snapshot in Longhorn is an object that represents content of a Longhorn volume at a particular moment. It is stored inside the cluster.
To programmatically create Longhorn snapshots, you can use the generic Kubernetes CSI VolumeSnapshot mechanism. To learn more about the CSI VolumeSnapshot mechanism, click here.
Prerequisite: CSI snapshot support needs to be enabled on your cluster. If your kubernetes distribution does not provide the kubernetes snapshot controller as well as the snapshot related custom resource definitions, you need to manually deploy them. For more information, see Enable CSI Snapshot Support.
To create a CSI VolumeSnapshot associated with a Longhorn snapshot, you first need to create a VolumeSnapshotClass
object
with the parameter type
set to snap
as follow:
kind: VolumeSnapshotClass
apiVersion: snapshot.storage.k8s.io/v1
metadata:
name: longhorn-snapshot-vsc
driver: driver.longhorn.io
deletionPolicy: Delete
parameters:
type: snap
For more information about VolumeSnapshotClass
, see the kubernetes documentation for VolumeSnapshotClasses.
After that, create a Kubernetes VolumeSnapshot
object with volumeSnapshotClassName
points to the name of the VolumeSnapshotClass
(longhorn-snapshot-vsc
) and
the source
points to the PVC of the Longhorn volume for which a Longhorn snapshot should be created.
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
name: test-csi-volume-snapshot-longhorn-snapshot
spec:
volumeSnapshotClassName: longhorn-snapshot-vsc
source:
persistentVolumeClaimName: test-vol
Result:
A Longhorn snapshot is created. The VolumeSnapshot
object creation leads to the creation of a VolumeSnapshotContent
Kubernetes object.
The VolumeSnapshotContent
refers to a Longhorn snapshot in its VolumeSnapshotContent.snapshotHandle
field with the name snap://volume-name/snapshot-name
.
To see the snapshot, click Volume in the top navigation bar and click the volume mentioned in the VolumeSnapshotContent.snapshotHandle
. Scroll down to see the list of all volume snapshots.
When the VolumeSnapshot object is created with kubectl, the VolumeSnapshot.uuid
field is used to identify a Longhorn snapshot and the associated VolumeSnapshotContent
object.
This creates a new Longhorn snapshot named snapshot-uuid
and the CSI request returns.
Afterwards a VolumeSnapshotContent
object named snapcontent-uuid
is created with the VolumeSnapshotContent.readyToUse
flag is set to true.
Create a PersistentVolumeClaim
object where the dataSource
field points to an existing VolumeSnapshot
object that is associated with Longhorn snapshot.
The csi-provisioner will pick this up and instruct the Longhorn CSI driver to provision a new volume with the data from the associated Longhorn snapshot.
An example PersistentVolumeClaim
is below. The dataSource
field needs to point to an existing VolumeSnapshot
object.
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: test-restore-pvc
spec:
storageClassName: longhorn
dataSource:
name: test-csi-volume-snapshot-longhorn-snapshot
kind: VolumeSnapshot
apiGroup: snapshot.storage.k8s.io
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 5Gi
Note that the spec.resources.requests.storage
value must be the same as the size of VolumeSnapshot
object.
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