Persistent Volumes and Claims

You deploy a PostgreSQL Pod. It works. You restart it. The data is gone. On the CKAD exam, you will be asked to fix exactly this problem: provision persistent storage, bind it to a claim, and mount it so data survives Pod restarts. The API surface is small, but the binding rules have subtleties that cost points if you get them wrong.

Kubernetes solves persistent storage with two API objects: PersistentVolume (PV) and PersistentVolumeClaim (PVC). The PV represents actual storage. The PVC is a request for storage. The separation is intentional: it decouples the person provisioning storage from the person consuming it. The CKAD exam tests this under the "Application Design and Build" domain (20%), specifically the "Utilize persistent and ephemeral volumes" competency.