Storage Concepts: Volumes, PVs, and PVCs

PostgreSQL needs its data directory. Redis with AOF persistence needs its append-only file. An ML training job needs its checkpoints. But containers are ephemeral by design: a crash, a restart, a rolling update, and the filesystem resets. Production workloads need storage that outlives the Pod.

Kubernetes solves this with a layered storage model. Ephemeral volumes handle scratch space and configuration injection. Persistent Volumes and Persistent Volume Claims separate what storage exists from what a workload needs. StorageClasses automate the provisioning so nobody has to create volumes by hand. Storage falls under the Container Orchestration domain (28% of the KCNA exam), and the exam expects you to understand how these layers connect.