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The OpenShift container platform uses the Kubernetes Persistent Volume (PV) framework, allowing cluster administrators to provide persistent storage for cluster operations that require data persistence. As a developer, you can use persistent volume claims (PVC) to request PV resources without having to understand the underlying storage infrastructure.

In this short guide, you will learn how to extend an existing PVC in OpenShift when using OpenShift container storage.Before extending a persistent volume, the StorageClass must have allowVolumeExpansion The field is set to true.

This is a list of storage classes available in the OpenShift cluster.

$ oc get sc
NAME                                  PROVISIONER                             RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
localblock                            kubernetes.io/no-provisioner            Delete          WaitForFirstConsumer   false                  186d
localfile                             kubernetes.io/no-provisioner            Delete          WaitForFirstConsumer   false                  186d
ocs-storagecluster-ceph-rbd           openshift-storage.rbd.csi.ceph.com      Delete          Immediate              false                  169d
ocs-storagecluster-cephfs (default)   openshift-storage.cephfs.csi.ceph.com   Delete          Immediate              true                   169d
openshift-storage.noobaa.io           openshift-storage.noobaa.io/obc         Delete          Immediate              false                  169d
thin                                  kubernetes.io/vsphere-volume            Delete          Immediate              false                  169d
unused                                kubernetes.io/no-provisioner            Delete          WaitForFirstConsumer   false                  190d

I will change the default storage class ocs-storagecluster-cephfs. Let’s export the configuration to a yaml file:

oc get sc ocs-storagecluster-cephfs -o yaml >ocs-storagecluster-cephfs.yml

I will modify the file to add the allowVolumeExpansion field.

allowVolumeExpansion: true
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  annotations:
    storageclass.kubernetes.io/is-default-class: "true"
  name: ocs-storagecluster-cephfs
parameters:
  clusterID: openshift-storage
  csi.storage.k8s.io/node-stage-secret-name: rook-csi-cephfs-node
  csi.storage.k8s.io/node-stage-secret-namespace: openshift-storage
  csi.storage.k8s.io/provisioner-secret-name: rook-csi-cephfs-provisioner
  csi.storage.k8s.io/provisioner-secret-namespace: openshift-storage
  fsName: ocs-storagecluster-cephfilesystem
provisioner: openshift-storage.cephfs.csi.ceph.com
reclaimPolicy: Delete
volumeBindingMode: Immediate
allowVolumeExpansion: true # Added field

Since SC is an immutable resource, please delete the currently configured storage class.

$ oc delete sc ocs-storagecluster-cephfs
storageclass.storage.k8s.io "ocs-storagecluster-cephfs" deleted

Apply the modified storage class configuration by running the following command:

$ oc apply -f ocs-storagecluster-cephfs.yml 
storageclass.storage.k8s.io/ocs-storagecluster-cephfs created

List the storage class to confirm that it has indeed been created.

$ oc get sc
NAME                                  PROVISIONER                             RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
localblock                            kubernetes.io/no-provisioner            Delete          WaitForFirstConsumer   false                  186d
localfile                             kubernetes.io/no-provisioner            Delete          WaitForFirstConsumer   false                  186d
ocs-storagecluster-ceph-rbd           openshift-storage.rbd.csi.ceph.com      Delete          Immediate              false                  169d
ocs-storagecluster-cephfs (default)   openshift-storage.cephfs.csi.ceph.com   Delete          Immediate              true                   5m20s
openshift-storage.noobaa.io           openshift-storage.noobaa.io/obc         Delete          Immediate              false                  169d
thin                                  kubernetes.io/vsphere-volume            Delete          Immediate              false                  169d
unused                                kubernetes.io/no-provisioner            Delete          WaitForFirstConsumer   false                  190d

Output Yalm and confirm that the new settings have been applied.

$ oc get sc ocs-storagecluster-cephfs -o yaml
allowVolumeExpansion: true
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"allowVolumeExpansion":true,"apiVersion":"storage.k8s.io/v1","kind":"StorageClass","metadata":{"annotations":{"storageclass.kubernetes.io/is-default-class":"true"},"name":"ocs-storagecluster-cephfs"},"parameters":{"clusterID":"openshift-storage","csi.storage.k8s.io/node-stage-secret-name":"rook-csi-cephfs-node","csi.storage.k8s.io/node-stage-secret-namespace":"openshift-storage","csi.storage.k8s.io/provisioner-secret-name":"rook-csi-cephfs-provisioner","csi.storage.k8s.io/provisioner-secret-namespace":"openshift-storage","fsName":"ocs-storagecluster-cephfilesystem"},"provisioner":"openshift-storage.cephfs.csi.ceph.com","reclaimPolicy":"Delete","volumeBindingMode":"Immediate"}
    storageclass.kubernetes.io/is-default-class: "true"
  creationTimestamp: "2020-10-31T13:33:56Z"
  name: ocs-storagecluster-cephfs
  resourceVersion: "242503097"
  selfLink: /apis/storage.k8s.io/v1/storageclasses/ocs-storagecluster-cephfs
  uid: 5aa95d3b-c39c-438d-85af-5c8550d6ed5b
parameters:
  clusterID: openshift-storage
  csi.storage.k8s.io/node-stage-secret-name: rook-csi-cephfs-node
  csi.storage.k8s.io/node-stage-secret-namespace: openshift-storage
  csi.storage.k8s.io/provisioner-secret-name: rook-csi-cephfs-provisioner
  csi.storage.k8s.io/provisioner-secret-namespace: openshift-storage
  fsName: ocs-storagecluster-cephfilesystem
provisioner: openshift-storage.cephfs.csi.ceph.com
reclaimPolicy: Delete
volumeBindingMode: Immediate

How to expand PVC in OpenShift

List the available PVCs in the namespace.

$ oc get pvc
NAME                                     STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS                AGE
data-harbor-harbor-redis-0               Bound    pvc-e516b793-60c5-431d-955f-b1d57bdb556b   1Gi        RWO            ocs-storagecluster-cephfs   169d
database-data-harbor-harbor-database-0   Bound    pvc-00a53065-9790-4291-8f00-288359c00f6c   2Gi        RWO            ocs-storagecluster-cephfs   169d
harbor-harbor-chartmuseum                Bound    pvc-405c68de-eecd-4db1-9ca1-5ca97eeab37c   5Gi        RWO            ocs-storagecluster-cephfs   169d
harbor-harbor-jobservice                 Bound    pvc-e52f231e-0023-41ad-9aff-98ac53cecb44   2Gi        RWO            ocs-storagecluster-cephfs   169d
harbor-harbor-registry                   Bound    pvc-77e159d4-4059-47dd-9c61-16a6e8b37a14   100Gi      RWX            ocs-storagecluster-cephfs   39d

Edit PVC and change capacity

$ oc edit pvc data-harbor-harbor-redis-0 
...
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 2Gi

Delete the advertising chain with copyright claims.

$ oc delete pods harbor-harbor-redis-0
pod "harbor-harbor-redis-0" deleted

Recreate the deployment declaring the storage, and the deployment should utilize the new capacity.

Expand PVC on OpenShift web console

You can also extend the PVC from the web console.

Click”Expand PVC” And set the required PVC capacity.

More articles about OpenShift.

How to deploy Ubuntu Pod in Kubernetes | OpenShift

Configure static IPv4 address in OpenShift 4.x CoreOS server

How to list and approve pending CSRs in OpenShift 4.x

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