PersistentVolumes

A PersistentVolume is a piece of durable storage in the cluster, independent of any Pod.

For data that must outlive Pods — a database's files, uploaded images — Kubernetes separates storage into two objects that snap together.

PV and PVC

  • A PersistentVolume (PV) is an actual piece of storage (a cloud disk, an NFS share). It is a cluster-wide resource, like a node.
  • A PersistentVolumeClaim (PVC) is a Pod's request for storage: "I need 5Gi that I can read and write."

Kubernetes binds a PVC to a suitable PV. The Pod mounts the PVC and never has to know the underlying disk details.

A Pod uses a PersistentVolumeClaim, which binds to a PersistentVolumePodmountsPVCrequest: 5GibindsPV10Gi cloud disk
Pod → PVC → PV. The claim is bound to a volume that provides the storage.

Example

Example · yaml
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-data
spec:
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: /mnt/data

When to use it

  • A database team creates PersistentVolumes backed by cloud SSD disks so that data persists even when the database pod is rescheduled to a different node.
  • A platform engineer pre-provisions PVs from a NAS device and makes them available for claim by any namespace in the cluster.
  • An operator checks a PV's reclaim policy to ensure it is set to Retain before deleting the associated PVC to prevent accidental data loss.

More examples

PersistentVolume manifest

Defines a 10 Gi PV with ReadWriteOnce access, Retain reclaim policy, and a hostPath backend for local testing.

Example · yaml
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-ssd-10gi
spec:
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Retain
  storageClassName: ssd
  hostPath:
    path: /mnt/data

List and describe PVs

Lists all PVs showing capacity, access modes, and status, then describes a specific PV to check if it is bound or available.

Example · bash
kubectl get pv
# NAME          CAPACITY  ACCESS MODES  RECLAIM POLICY  STATUS
# pv-ssd-10gi   10Gi      RWO           Retain          Available

kubectl describe pv pv-ssd-10gi | grep -E 'Capacity|Status|Claim'

Check PV binding after claim

Shows the two-way binding relationship: after a PVC is created, both the PV and PVC show Bound status and reference each other.

Example · bash
kubectl apply -f pvc.yaml
kubectl get pv pv-ssd-10gi
# STATUS: Bound
# CLAIM: default/my-pvc

kubectl get pvc my-pvc
# STATUS: Bound  VOLUME: pv-ssd-10gi

Related

k8s pvck8s storageclass

Discussion

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