Persistent Volumes in Kubernetes

1. What is a Persistent Volume (PV)?

A Persistent Volume is a pre-provisioned storage resource in the cluster. It can come from a variety of backends:

• Local disk
• NFS (Network File System)
• GCP Persistent Disk
• AWS EBS
• Azure Disk, etc.

Think of it like a physical hard drive that Kubernetes can plug into Pods.

apiVersion: v1
kind: PersistentVolume
metadata:
  name: my-pv
spec:
  capacity:
    storage: 1Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: /mnt/data

---

2. What is a Persistent Volume Claim (PVC)?

A Persistent Volume Claim is a request for storage by a user (or Pod). The claim specifies:

• How much storage is needed
• Access mode (ReadWriteOnce, ReadOnlyMany, ReadWriteMany)

Kubernetes then binds the PVC to a suitable PV.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 500Mi

---

3. How Pod Uses a PVC

A Pod doesn't mount the PV directly. Instead, it mounts the PVC, which abstracts the underlying storage.

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  containers:
    - name: app
      image: busybox
      command: ["sh", "-c", "echo 'Hello' >> /data/out.txt && sleep 3600"]
      volumeMounts:
        - mountPath: /data
          name: storage
  volumes:
    - name: storage
      persistentVolumeClaim:
        claimName: my-pvc

---

Access Modes

• ReadWriteOnce

  • Description: Mounted as read-write by a single node

• ReadOnlyMany

  • Description: Mounted as read-only by many nodes

• ReadWriteMany

  • Description: Mounted as read-write by many nodes

---

Use Case Examples

• Database

  • Description: Store DB files on persistent disk

• Logging

  • Description: Store logs even if Pod restarts

• Uploads

  • Description: Save user-uploaded files outside container lifecycle

---

Summary

• PV: The physical or cloud storage abstraction.
• PVC: A request for storage.
• Pod uses PVC to persist data.