Chapter 8. Expanding persistent volumes

Procedure

• Edit the StorageClass object and add the allowVolumeExpansion attribute by running the following command:

  $ oc edit storageclass <storage_class_name>

  Enter the name of storage class in <storage_class_name>.

  The following example shows adding this line at the bottom of the storage class configuration.

  Example storage class YAML file with allowVolumeExpansion field set to true

  apiVersion: storage.k8s.io/v1
  kind: StorageClass
  ...
  parameters:
    type: gp2
  reclaimPolicy: Delete
  allowVolumeExpansion: true

  • parameters.allowVolumeExpansion: Setting this field to true allows persistent volume claims (PVCs) to be expanded after creation.

Prerequisites

• The underlying CSI driver supports resize.

  For information about which CSI drivers support resizing, see under the Additional resources section "CSI drivers supported by OpenShift Container Platform".

• Dynamic provisioning is used.

• The controlling StorageClass object has allowVolumeExpansion set to true.

  For more information, see section Enabling volume expansion support.

Procedure

• For the persistent volume claim (PVC), set .spec.resources.requests.storage to the desired new size.

Verification

• To confirm that the resize is finished, look at the status.conditions field of the PVC . OpenShift Container Platform adds the Resizing condition to the PVC during expansion, which is removed after expansion completes.

Prerequisites

• The underlying volume driver supports resize.

  For information about which CSI drivers support resizing, see under the Additional resources section "CSI drivers supported by OpenShift Container Platform".

• The driver is set with the RequiresFSResize capability to true. The FlexVolume can then be expanded after restarting the pod.
• Dynamic provisioning is used.

• The controlling StorageClass object has allowVolumeExpansion set to true.

  For more information, see section Enabling volume expansion support.

Procedure

• To use resizing in the FlexVolume plugin, you must implement the ExpandableVolumePlugin interface using these methods:

  • RequiresFSResize

    If true, updates the capacity directly. If false, calls the ExpandFS method to finish the filesystem resize.

  • ExpandFS

    If true, calls ExpandFS to resize filesystem after physical volume expansion is done. The volume driver can also perform physical volume resize together with filesystem resize.

Prerequisites

• The controlling storage class has the allowVolumeExpansion field set to true.

  For more information, see section Enabling volume expansion support.

Procedure

• Edit the PVC and request a new size by editing spec.resources.requests. For example, the following expands the ebs PVC to 8 Gi:

  Example PVC YAML file

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

  Where updating spec.resources.requests to a larger amount expands the PVC.

• Check the condition by running the following command:

  $ oc describe pvc <pvc_name>

• ControllerResizeInProgress: Controller resize attempt is in progress.
• ControllerResizeFailed: Controller resize attempt failed.
• NodeResizeInProgress: Node resize attempt is in progress.
• NodeResizeFailed: Node resize attempt failed.