Persistent Volumes

Persistent Volumes — Storage That Survives

A PersistentVolume (PV) is a piece of storage in the cluster that has been provisioned by an administrator or dynamically provisioned using StorageClasses. It exists independently of any Pod.

A PersistentVolumeClaim (PVC) is a request for storage by a user. Pods use PVCs to claim PVs — like filling out a storage request form.

PV and PVC Workflow

  Admin provisions storage          User creates a PVC
  ┌─────────────────────┐          ┌─────────────────────┐
  │  PersistentVolume    │          │  PersistentVolume   │
  │  (PV)               │◀────────▶│  Claim (PVC)        │
  │  10Gi SSD, RWO      │  binds   │  "I need 5Gi"       │
  └─────────────────────┘          └──────────┬──────────┘
                                              │
                                     Pod uses the PVC
                                     ┌─────────┴─────────┐
                                     │  volumeMounts:    │
                                     │    name: data     │
                                     │    mountPath: /data│
                                     └───────────────────┘

Creating a PersistentVolume

apiVersion: v1
kind: PersistentVolume
metadata:
  name: my-pv
spec:
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Retain
  storageClassName: standard
  hostPath:
    path: /mnt/data

accessModes — ReadWriteOnce (one node), ReadOnlyMany (many nodes), ReadWriteMany (many nodes, not all storage supports this).

reclaimPolicy — Retain (keep data when PVC is deleted) or Delete (delete the storage).

Creating a PersistentVolumeClaim

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi
  storageClassName: standard

Kubernetes matches this PVC to a PV with sufficient capacity and compatible access modes.

Using a PVC in a Pod

apiVersion: v1
kind: Pod
metadata:
  name: my-app
spec:
  containers:
    - name: app
      image: my-app
      volumeMounts:
        - name: storage
          mountPath: /var/data
  volumes:
    - name: storage
      persistentVolumeClaim:
        claimName: my-pvc

The data in /var/data persists even if the Pod is deleted. A new Pod can claim the same PVC and access the data.

Dynamic Provisioning

# With a StorageClass, PVs are created on demand
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: fast
provisioner: kubernetes.io/aws-ebs
parameters:
  type: gp3
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer

Dynamic provisioning eliminates the need for admins to manually create PVs. When a PVC references a StorageClass, the storage is automatically provisioned.