ストレージクラスと動的プロビジョニング

With static provisioning an admin must pre-create a PersistentVolume for every claim. That does not scale and wastes capacity when claims do not match exactly.

A StorageClass describes a kind of storage and a provisioner. When a PVC requests that class, Kubernetes creates a matching PersistentVolume automatically.

Key fields are the provisioner, backend-specific parameters, and policies like reclaimPolicy and volumeBindingMode.

A PVC just names the StorageClass; no PV needs to exist beforehand.

A cluster can mark one StorageClass as default. PVCs that omit storageClassName then use it automatically.

Delete removes the underlying disk when the PVC is deleted; Retain keeps it so you can recover data manually.

WaitForFirstConsumer delays creating the volume until a Pod is scheduled, so the disk lands in the same zone as the Pod, avoiding cross-zone attach failures.

If allowVolumeExpansion: true, you can grow a PVC by editing its requested size.

Offer several classes, such as fast SSD and cheap HDD, and let teams pick the right cost/performance tradeoff per workload.

Modern provisioners use the Container Storage Interface (CSI), a standard plugin model so any storage vendor can integrate without changing Kubernetes core.

After creating the PVC, watch it become Bound and see the auto-created PV.

You learned how StorageClasses enable dynamic provisioning, the meaning of reclaimPolicy and volumeBindingMode, volume expansion, CSI drivers, and how PVCs bind to auto-created PVs.