Shrink Kubernetes persistent volumes

I do have multiple persistent volumes which need to be shrinked to reduce the hosting costs. I already figured out that Kubernetes does not provide such an option. I also tried to clone or the restore the volumes from an snapshot to a new smaller volume - with the same result (requested volume size XXX is less than the size XXX for the source snapshot).

Nevertheless I need a solution or workaround to get this done.

The cluster is deployed with Rancher and the volumes are mounted to a Ceph Cluster. Everything is provided by an external hoster.

Finally I achieved what needed with the following steps (still tricky and manual work):

• Stop running pod (otherwhise you could not use the volume in the next steps)
• Create the a new PVC with the desired capacity (ensure that the spec and label matches the exisitng PVC)
• Run this Job https://github.com/edseymour/pvc-transfer
  • In the spec of the job-template.yaml set the source and destination volume
• Set the ReclaimPolicy on the new created pv to Retain. This will ensure that the pv won't be deleted after we delete the temp pvc in the next step
• Delete the source and destination pvc
• Create a new pvc with the old name and the new storage capacity
• On the new pv point the claimRef to the new pvc