Volume Group Snapshots

Ceph provides the ability to create crash-consistent snapshots of multiple volumes. A group snapshot represents “copies” from multiple volumes that are taken at the same point in time. A group snapshot can be used either to rehydrate new volumes (pre-populated with the snapshot data) or to restore existing volumes to a previous state (represented by the snapshots)

Prerequisites¶

Install the snapshot controller, volume group snapshot and snapshot CRDs, refer to VolumeGroupSnapshot documentation here for more details.
A VolumeGroupSnapshotClass is needed for the volume group snapshot to work. The purpose of a VolumeGroupSnapshotClass is defined in the kubernetes documentation. In short, as the documentation describes it:

Info

Created by cluster administrators to describe how volume group snapshots should be created. including the driver information, the deletion policy, etc.

Volume Group Snapshots¶

CephFS VolumeGroupSnapshotClass¶

In VolumeGroupSnapshotClass, the csi.storage.k8s.io/group-snapshotter-secret-name parameter should reference the name of the secret created for the cephfs-plugin.

In the VolumeGroupSnapshotClass, update the value of the clusterID field to match the namespace that Rook is running in. When Ceph CSI is deployed by Rook, the operator will automatically maintain a configmap whose contents will match this key. By default this is "rook-ceph".

1	`kubectl create -f deploy/examples/csi/cephfs/groupsnapshotclass.yaml`

CephFS VolumeGroupSnapshot¶

In VolumeGroupSnapshot, volumeGroupSnapshotClassName should be the name of the VolumeGroupSnapshotClass previously created. The labels inside matchLabels should be present on the PVCs that are already created by the CephFS CSI driver.

1	`kubectl create -f deploy/examples/csi/cephfs/groupsnapshot.yaml`

Verify CephFS GroupSnapshot Creation¶

$ kubectl get volumegroupsnapshotclass
NAME                              DRIVER                          DELETIONPOLICY   AGE
csi-cephfsplugin-groupsnapclass   rook-ceph.cephfs.csi.ceph.com   Delete           21m

$ kubectl get volumegroupsnapshot
NAME                       READYTOUSE   VOLUMEGROUPSNAPSHOTCLASS          VOLUMEGROUPSNAPSHOTCONTENT                              CREATIONTIME   AGE
cephfs-groupsnapshot       true         csi-cephfsplugin-groupsnapclass   groupsnapcontent-d13f4d95-8822-4729-9586-4f222a3f788e   5m37s          5m39s

The snapshot will be ready to restore to a new PVC when READYTOUSE field of the volumegroupsnapshot is set to true.

Restore the CephFS volume group snapshot to a new PVC¶

Find the name of the snapshots created by the VolumeGroupSnapshot first by running:

$ kubectl get volumesnapshot -o=jsonpath='{range .items[?(@.metadata.ownerReferences[0].name=="cephfs-groupsnapshot")]}{.metadata.name}{"\n"}{end}'
snapshot-a79d08c7b7e18953ec321e77be9c9646234593411136a3671d72e8a26ffd419c

It will list the names of the snapshots created as part of the group.

In pvc-restore, dataSource should be one of the Snapshot that we just found. The dataSource kind should be the VolumeSnapshot.

Create a new PVC from the snapshot

1	`kubectl create -f deploy/examples/csi/cephfs/pvc-restore.yaml`

Verify CephFS Restore PVC Creation¶

$ kubectl get pvc
cephfs-pvc           Bound    pvc-9ae60bf9-4931-4f9a-9de1-7f45f31fe4da   1Gi        RWO            rook-cephfs    <unset>                 171m
cephfs-pvc-restore   Bound    pvc-b4b73cbb-5061-48c7-9ac8-e1202508cf97   1Gi        RWO            rook-cephfs    <unset>                 46s

CephFS volume group snapshot resource Cleanup¶

To clean the resources created by this example, run the following:

kubectl delete -f deploy/examples/csi/cephfs/pvc-restore.yaml
kubectl delete -f deploy/examples/csi/cephfs/groupsnapshot.yaml
kubectl delete -f deploy/examples/csi/cephfs/groupsnapshotclass.yaml