A volume is considered to be offline when it is not attached to a node or pod. Both types of clusters, Supervisor Clusters and Tanzu Kubernetes clusters, support offline volume expansion.

Prerequisites

Make sure to upgrade your vSphere environment to an appropriate version that supports offline volume expansion. See Volume Expansion in vSphere with Tanzu.

Procedure

  1. Create a persistent volume claim (PVC) with a storage class.
    1. Define a PVC using the following YAML manifest as an example.
      In the example, the size of the requested storage is 1 Gi. 
      apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: example-block-pvc
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi
  storageClassName: example-block-sc
    2. Apply the PVC to the Kubernetes cluster. 
      kubectl apply -f example-block-pvc.yaml
  2. Patch the PVC to increase its size.
    If the PVC is not attached to a node or being used by a pod, use the following command to patch the PVC. In this example, the requested storage increase is 2 Gi. 
    kubectl patch pvc example-block-pvc -p '{"spec": {"resources": {"requests": {"storage": "2Gi"}}}}'
    This action triggers an expansion in the volume associated with the PVC.
  3. Verify that the size of the volume has increased. 
    kubectl get pv
NAME                                       CAPACITY ACCESS MODES RECLAIM POLICY STATUS   CLAIM                       STORAGECLASS           REASON AGE
pvc-9e9a325d-ee1c-11e9-a223-005056ad1fc1   2Gi           RWO         Delete     Bound    default/example-block-pvc   example-block-sc              6m44s
    Note: The size of the PVC remains unchanged until the PVC is used by a pod.
    The following example shows that the PVC size hasn't changed. If you describe the PVC, you can see the FilesystemResizePending condition applied on the PVC. 
    kubectl get pvc
NAME                STATUS VOLUME                                     CAPACITY ACCESS MODES   STORAGECLASS       AGE
example-block-pvc   Bound  pvc-9e9a325d-ee1c-11e9-a223-005056ad1fc1   1Gi           RWO       example-block-sc   6m57s
  4. Create a pod to use the PVC.
    When the PVC is used by the pod, the filesystem is expanded.
  5. Verify that the size of the PVC has been modified. 
    kubectl get pvc
NAME                STATUS VOLUME                                    CAPACITY ACCESS MODES STORAGECLASS     AGE
example-block-pvc   Bound  pvc-24114458-9753-428e-9c90-9f568cb25788   2Gi         RWO      example-block-sc 2m12s
    The FilesystemResizePending condition has been removed from the PVC. Volume expansion is complete.

What to do next

A vSphere administrator can see the new volume size in the vSphere Client. See Monitor Persistent Volumes in the vSphere Client.