Using volume expansion

In Google Kubernetes Engine (GKE), you can use the Kubernetes volume expansion feature to easily change a persistent volume's capacity after its creation.

Prerequisites

Volume expansion has the following prerequisites:

  • If the volume you want to resize is managed by a CSI Driver:
    • Ensure the GKE cluster version is 1.16 or greater.
    • Check your storage vendor's documentation to verify your CSI driver supports volume expansion (the Compute Engine persistent disk CSI Driver does).
  • If the volume you want to resize is managed by an in-tree volume plugin:
    • Ensure the GKE cluster version is 1.11 or greater. While GKE cluster versions 1.11-1.14 support expansion of volumes managed by in-tree plugins, they require all Pods using the volume to be terminated and recreated to complete volume expansion.
    • Check your storage vendor's documentation to verify your in-tree volume plugin supports volume expansion (the Compute Engine persistent disk in-tree plugin does).

Using volume expansion

To use volume expansion, perform the following tasks:

  1. Add allowVolumeExpansion: true to your StorageClass, if your StorageClass doesn't already have the field. For example:

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: standard
provisioner: my.driver
...
allowVolumeExpansion: true

  2. Request a change in volume capacity by editing your PersistentVolumeClaim's spec.resources.requests.storage field. For example, you could change the following PVC from having a 30 gibibyte (GiB) disk to having a 40 GiB disk.

    Before editing:

     # pvc-demo.yaml
 apiVersion: v1
 kind: PersistentVolumeClaim
 metadata:
   name: pvc-demo
 spec:
   accessModes:
     - ReadWriteOnce
   resources:
     requests:
       storage: 30Gi

    After editing:

     # pvc-demo.yaml
 apiVersion: v1
 kind: PersistentVolumeClaim
 metadata:
   name: pvc-demo
 spec:
   accessModes:
     - ReadWriteOnce
   resources:
     requests:
       storage: 40Gi

  3. Verify the change by viewing PVC. To view your PVC, run the following command:

    kubectl get pvc pvc-name -o yaml

    Eventually, you should see the new volume in the status.capacity field. For example:

    ...
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 40Gi
  storageClassName: standard
  volumeMode: Filesystem
  volumeName: pvc-078b7484-cc8d-4077-9bcb-2c17d8d4550c
status:
  accessModes:
  - ReadWriteOnce
  capacity:
    storage: 40Gi
...

What's next