Ability to clone and restore volumes across different Ceph CSI storage classes - Dev Preview

Problem Statement

• To transition a persistent volume claim (PVC) to another when Ceph cluster has pools with multiple device classes or pools with different failure-domain rules. For example, to take a volume snapshot of a PVC from rbd-ssd StorageClass, clone it to rbd-hdd, and delete the snapshot on the more expensive StorageClass.
• To take a snapshot of an image on a storage class that has lower failure-domain tolerance, and clone it to a StorageClass that has higher failure-domain tolerance.
• To reduce storage footprint.
• To move from a storage class with replica 3 to replica 2 or replica 1 there is already existing high availability or underlying storage providing resiliency.

Solution

You now have the ability to take a snapshot of a PVC created with one Ceph-CSI storage class and clone it to a PVC created using another Ceph-CSI StorageClass. The following parameters are supported for cross-storage clone or restore:

• Clonning/Restore PVC across different pool in case of RBD
• Clonning/Restore PVC across different filesystem in case of CephFS

Cloning/Restoring a PVC

Procedure

To clone/restore a PVC, you can use a StorageClass for the PVC clone other than the parent class.

1. Save a YAML file similar to the following with a file name such as pvc.yaml.

Example PVC YAML:

# pvc.yaml: 1GB volume of the rbd-ssd StorageClass
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
 name: rbd-pvc
spec:
 accessModes:
   - ReadWriteOnce
 resources:
   requests:
     storage: 1Gi
 storageClassName:   rbd-ssd

2. Run the following command to create the rbd-pvc:

# oc create -f pvc.yaml

3. Save a YAML file similar to the following with a file name such as pvc-clone.yaml.

Example PVC-Clone YAML:

# pvc-clone.yaml: create a rbd-pvc-clone volume of StorageClass rbd-hdd with the data from rbd-pvc
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
 name: rbd-pvc-clone
spec:
 storageClassName: rbd-hdd
 dataSource:
   name: rbd-pvc
   kind: PersistentVolumeClaim
 accessModes:
   - ReadWriteOnce
 resources:
   requests:
     storage: 1Gi

4. Run the following command to create the rbd-pvc-clone:

# oc create -f pvc-clone.yaml

As a different StorageClass is used while cloning the PVC, you can specify pool as per your requirement.

5. Save a YAML file similar to the following with a file name such as sc.yaml.

Example parent StorageClass:

# sc.yaml: rbd-ssd StorageClass using Ceph pool with only SSD devices
metadata:
  name: rbd-ssd
provisioner: openshift-storage.rbd.csi.ceph.com
parameters:
    clusterID: openshift-storage
    pool: ocs-storagecluster-cephblockpool

6. Run the following command to create the StorageClass:

# oc create -f sc.yaml

You can create your own pool with the required replica count as per your requirement. This enables you to clone or restore the volume with a set of parameters other than that of the parent volume.

The StorageClass also enables you to clone an encrypted PVC with different encryption configurations.

Example parent StorageClass with encryption:

# sc-encrypt.yaml: ...
metadata:
  name: rbd-hdd
provisioner: 
openshift-storage.rbd.csi.ceph.com
parameters:
    clusterID: openshift-storage
    pool: ocs-storagecluster-cephblockpool
encrypted: ‘true’
encryptionKMSID: vaultKMS

7. Run the following command to create the new StorageClass:

# oc create -f sc-encrypt.yaml

You can change the encryptionKMSID as per your requirement.

NOTE: You can clone or restore CephFS PVC across a different file system similar to the RBD PVC example provided above.