How to resize a PVC

Created by Steve Place, Modified on Thu, Feb 13 at 4:13 PM by Steve Place

First, check what storage class your PVC is using:

> kubectl get pvc -n <namespace>
NAME         STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
my-pvc       Bound    pvc-12345678-90ab-cdef-1234-567890abcdef   10Gi       RWO            longhorn       5d

In this example, our storage class is longhorn. We need to see if it can be resized. To do that, we'll run:

> kubectl get storageclass longhorn -o=jsonpath='{.allowVolumeExpansion}'

If this returns true, we're able to resize the PVC. If you see false or get no output, you can either choose a storage class that supports expansion (see your cloud provider's documentation for examples) or edit the storage class to allow expansion (covered in the Appendix).

Now that we have a PVC that supports expansion, we need to edit it:

> kubectl edit pvc <pvc-name> -n <namespace>

Look for the spec.resources.requests.storage field and modify it to the desired size. For example, change:

spec:
  resources:
    requests:
      storage: 10Gi

to:

spec:
  resources:
    requests:
      storage: 20Gi

or whatever value you prefer. Save and exit the editor.

Now verify the change took effect:

> kubectl get pvc <pvc-name> -n <namespace>
NAME      STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
my-pvc    Bound    pvc-12345678-90ab-cdef-1234-567890abcdef   20Gi       RWO            longhorn       5d

You can see that CAPACITY has be increased to 20Gi, which we were expecting. (Note it may take a few seconds to few minutes for the change to take effect.)

If the PVC is in the Pending status or the size hasn't changed, check for errors with:

kubectl describe pvc <pvc-name> -n <namespace>

After resizing, delete the Stardog pod using the PVC to force a restart. This ensures the Stardog pod will recognize the PVC's new capacity.

> kubectl delete pod <stardog-pod-name> -n <namespace>

Appendix

How to enable volume expansion in a storage class

The following steps show how to edit an existing storage class, but you can also use them to create a new storage class if you would prefer not to overwrite the old one.

You cannot edit a storage class directly in Kubernetes, so you'll need to delete and recreate it.

First export your current configuration to a YAML file:

> kubectl get storageclass longhorn -o yaml > longhorn-sc.yaml

In this example, the storage class is longhorn, but replace this with whatever your storage class is. Next, open your saved yaml file with a text editor and add/update the allowVolumeExpansion field:

allowVolumeExpansion: true

A correctly modified storage class YAML file will look something like this:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: longhorn
provisioner: driver.longhorn.io
reclaimPolicy: Delete
volumeBindingMode: Immediate
allowVolumeExpansion: true

Since storage classes cannot be edited in place, you must delete the old one. Be careful - this won’t affect existing PVCs, but any new PVCs won’t have a storage class until you recreate it:

kubectl delete storageclass longhorn

Now recreate the storage class using our modified YAML file:

kubectl apply -f longhorn-sc.yaml

Finally, check to make sure our new class allows for volume expansion:

kubectl get storageclass longhorn -o=jsonpath='{.allowVolumeExpansion}'