Often, it can be attractive to allow end users to configure the sizing of PVCs in a Kubernetes Cluster. While Rook/Ceph intends to support resizable PVCs in a future release, many kubernetes workload types that use PVCs, e.g. StatefulSet volumeClaimTemplates have immutable fields and do not support patching the volume claim size.
The recommendation in this case, when using Rook/Ceph-backed PVCs, is to request a volume much larger than the desired size. Because Rook PVCs are backed by an object store, they are sparse, and won’t actually consume disk space until that space is consumed in by the workload using the PVC.