Expand persistent volume claim volume size

Persistent volume size can be expanded by modifying storage attribute in persistent volume claim object. Storage size can't be shrunken. Upcloud's CSI driver only supports offline expansion so the application needs to be scaled down before operation.

Expanding persistent volume requires following steps:

• take data backup!
• shut down application that uses persistent volume that is going to be resized
• patch PVC object with new size
• when resize is done, start application(s)

Prerequisites

• kubectl installed
• cluster config (kubeconfig)

This document uses a mariadb deployment from the guide on Persistent Volumes as an example.
Goal here is to resize the MariaDB data partition from 10GB to 20GB.

Shut down application

Shut down the application that uses PVC that is going to be resized. This will detach the storage device from the worker node and allow the back-end to resize the storage.

Check current partition size using df command

$ kubectl exec -it deployments/mariadb -- df -h /var/lib/mysql
Filesystem      Size  Used Avail Use% Mounted on
/dev/vdb1       9.8G  148M  9.1G   2% /var/lib/mysql

Size should be close to what was defined in volume.yaml manifest, which was 10GB in the MariaDB example.

$ kubectl -n default scale deployment mariadb --replicas=0
deployment.apps/mariadb scaled

Patch PVC object with new size

$ kubectl patch pvc mariadb-pvc -p '{"spec":{"resources":{"requests":{"storage": "20Gi"}}}}'
persistentvolumeclaim/mariadb-pvc patched

New size can be also updated directly to volume.yaml manifest and then re-apply using kubectl apply -f volume.yaml

This might take some time. Process can be monitored by checking mariadb-pvc events:

$ kubectl describe pvc mariadb-pvc

There should be an event message Resize volume succeeded when operation is done.

Start application

$ kubectl -n default scale deployment mariadb --replicas=1
deployment.apps/mariadb scaled

Confirm the new size

$ kubectl exec -it deployments/mariadb -- df -h /var/lib/mysql
Filesystem      Size  Used Avail Use% Mounted on
/dev/vdb1        20G  148M   19G   1% /var/lib/mysql

This is just a raw example. You might need to e.g. optimise table(s) to make the database engine aware of the extended space.