Expanding

Expanding a Persistent Volume (PV) in Kubernetes allows to increase the size of a volume without downtime, ensuring applications continue running with sufficient storage. Simplyblock supports online expansion of Logical Volumes (LVs) through its CSI driver, making it possible to resize volumes dynamically as storage requirements grow.

Info

To enable volume expansion Kubernetes 1.16 or later is required.

Enable Volume Expansion

To enable volume expansion, the StorageClass has to be configured accordingly. To enable volume expansion, the property allowVolumeExpansion has to be set to true.

Allowing volume expansion in StorageClass

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: encrypted-volumes
provisioner: csi.simplyblock.io
parameters:
  encryption: "True"
  csi.storage.k8s.io/fstype: ext4
  ... other parameters
reclaimPolicy: Delete
volumeBindingMode: Immediate
allowVolumeExpansion: true # <- Enable volume expansion

Expand a PersistentVolume

To expand an existing volume, update the field spec.resources.requests.storage in the existing resource descriptor.

Updating the volume size

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-example-pvc
spec:
  resources:
    requests:
      storage: 500Gi # <- Was 100Gi before

Then apply the change.

Apply resource update

kubectl apply -f pvc.yaml

Resize the Filesystem (If Required)

Certain filesystems, such as ext4, may require growing the filesystem after the underlying volume has been expanded. This can usually be handled automatically by the CSI driver or may require running filesystem-specific commands within the pod.

Shrinking a Volume

Theoretically it is possible to shrink a volume. It can, however, create issues with certain filesystems. When a volume needs to be shrunk, it is recommended to create a snapshot and restore it onto a new volume.