Chapter 28. Expanding Persistent Volumes

To allow expansion of persistent volume claims (PVC) by OpenShift Container Platform users, OpenShift Container Platform administrators must create or update a StorageClass with allowVolumeExpansion set to true. Only PVCs created from that class are allowed to expand.

For example, OpenShift Container Platform administrators can add the allowVolumeExpansion attribute to the StorageClass’s configuration:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: gluster-container
provisioner: kubernetes.io/glusterfs
parameters:
  resturl: "http://heketi-storage-project.cloudapps.mystorage.com"
  restuser: "admin"
  secretNamespace: "default"
  secretName: "heketi-secret"
allowVolumeExpansion: true

Once the OpenShift Container Platform administrator has created a StorageClass with allowVolumeExpansion set to true, you can create a PVC from that class, and afterwards, whenever needed, you can edit the PVC and request a new size.

For example:

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: gluster-mysql
spec:
  storageClass: "storageClassWithFlagSet"
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 8Gi 1

Expanding PVCs based on volume types that need file system resizing (such as GCE PD, EBS, and Cinder) is a two-step process. This process usually involves expanding volume objects in the CloudProvider, and then expanding the file system on the actual node.

Expanding the file system on the node only happens when a new pod is started with the volume.

The following process assumes that the PVC was previously created from a StorageClass with allowVolumeExpansion set to true:

  oc describe pvc <pvc_name>

When the CloudProvider object has finished resizing, the persistent volume (PV) object reflects the newly requested size in PersistentVolume.Spec.Capacity. At this point, you can create or re-create a new pod from the PVC to finish the file system resizing. Once the pod is running, the newly requested size is available and FileSystemResizePending condition is removed from the PVC.

If expanding underlying storage fails either on master or node, the OpenShift Container Platform administrator can manually recover the PVC state and cancel the resize requests that are continuously retried by the controller without administrator intervention.

Currently, this can be done manually by completing the following steps: