Increase the pvc size in a statefulset

In order to increase the desired size of a volumeClaimTemplates in a kubernetes statefulset, if we only change the size, we wil get this error:

recreating StatefulSet because the update operation wasn't possible
...
Forbidden: updates to statefulset spec for fields other than 'replicas', 'ordinals', 'template', 'updateStrategy', 'persistentVolumeClaimRetentionPolicy' and 'minReadySeconds' are forbidden"

This is because that field is inmutable.

If we can lose data, we can simply delete the statefulset and create it again with the desired size. But if we want to maintain the data the steps can be:

Disable autosync

If using autosync in argocd or similar tools, disable autosync

Increase the size in the PVC

Edit the PVC manually and change the size with

kubectl edit pvc NAME-OF-THE-PVC

And the wait until it has been resized.

kubectl get pvc NAME-OF-THE-PVC -w

This step needs to have an storageclass with allowVolumeExpansion supported by the storagebackend and enabled in our storageclass definition

Do an orphan delete of the statefulset

Next we will delete the statefulset via

kubectl delete sts --cascade=orphan STATEFULSET

This will not delete the pods and PVC

Reapply the statefulset with the new size

Finally apply the manifest with the new size

kubectl apply -f STATEFULSET

If using argocd or similar tool, change the size in the manifest, and do a syn of the statefulset. Enable autosync again