How to Create Persistent Volumes and Persistent Volume Claims in Kubernetes

This guide explains how to create and manage persistent storage in Kubernetes using Persistent Volumes (PV) and Persistent Volume Claims (PVC).

Prerequisites

• Running Kubernetes cluster
• kubectl installed and configured
• Storage provider (local disk, NFS, cloud provider, etc.)

Understanding PV and PVC

Persistent Volume (PV)

• Piece of storage in the cluster
• Provisioned by administrator
• Lifecycle independent of pods

Persistent Volume Claim (PVC)

• Storage request by user
• Claims can request specific size and access modes
• Binds to a PV

Creating a Persistent Volume

Local Storage PV

apiVersion: v1
kind: PersistentVolume
metadata:
  name: local-pv
spec:
  capacity:
    storage: 10Gi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Retain
  storageClassName: local-storage
  local:
    path: /mnt/data
  nodeAffinity:
    required:
      nodeSelectorTerms:
      - matchExpressions:
        - key: kubernetes.io/hostname
          operator: In
          values:
          - worker-node1

NFS PV

apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs-pv
spec:
  capacity:
    storage: 5Gi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Recycle
  storageClassName: nfs
  nfs:
    path: /mnt/data
    server: nfs-server.example.com

Creating a Persistent Volume Claim

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

Using PVC in Pods

apiVersion: v1
kind: Pod
metadata:
  name: mysql-pod
spec:
  containers:
  - name: mysql
    image: mysql:5.7
    volumeMounts:
    - name: mysql-storage
      mountPath: /var/lib/mysql
  volumes:
  - name: mysql-storage
    persistentVolumeClaim:
      claimName: mysql-pvc

Access Modes

1. ReadWriteOnce (RWO)

2. Volume mounted as read-write by single node

3. ReadOnlyMany (ROX)

4. Volume mounted read-only by many nodes

5. ReadWriteMany (RWX)

6. Volume mounted as read-write by many nodes

Reclaim Policies

1. Retain
2. Keeps data when PVC is deleted

3. Requires manual cleanup

4. Delete

5. Deletes PV and data when PVC is deleted

6. Recycle

7. Basic scrub (rm -rf) before reuse
8. Deprecated in favor of dynamic provisioning

Dynamic Provisioning

Storage Class Definition

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: fast
provisioner: kubernetes.io/aws-ebs
parameters:
  type: gp2
  fsType: ext4

PVC with Storage Class

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: dynamic-pvc
spec:
  accessModes:
    - ReadWriteOnce
  storageClassName: fast
  resources:
    requests:
      storage: 10Gi

Production Example

Stateful Application with PV/PVC

---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: postgres-pv
  labels:
    type: local
spec:
  storageClassName: manual
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/mnt/data"
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: postgres-pvc
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: postgres
spec:
  serviceName: postgres
  replicas: 1
  selector:
    matchLabels:
      app: postgres
  template:
    metadata:
      labels:
        app: postgres
    spec:
      containers:
      - name: postgres
        image: postgres:13
        env:
        - name: POSTGRES_DB
          value: myapp
        - name: POSTGRES_USER
          valueFrom:
            secretKeyRef:
              name: postgres-secrets
              key: username
        - name: POSTGRES_PASSWORD
          valueFrom:
            secretKeyRef:
              name: postgres-secrets
              key: password
        ports:
        - containerPort: 5432
          name: postgres
        volumeMounts:
        - name: postgres-storage
          mountPath: /var/lib/postgresql/data
      volumes:
      - name: postgres-storage
        persistentVolumeClaim:
          claimName: postgres-pvc

Best Practices

1. Storage Planning

• Size volumes appropriately
• Consider I/O requirements
• Plan for scalability

2. Data Protection

• Use appropriate reclaim policies
• Implement backup solutions
• Consider disaster recovery

3. Performance

• Choose appropriate storage class
• Monitor storage usage
• Consider I/O patterns

Common Operations

Managing PVs and PVCs

# List PVs
kubectl get pv

# List PVCs
kubectl get pvc

# Describe PV
kubectl describe pv pv-name

# Describe PVC
kubectl describe pvc pvc-name

Volume Operations

# Check volume usage
kubectl exec pod-name -- df -h

# Copy data to/from volumes
kubectl cp /local/path pod-name:/container/path

Troubleshooting

Common Issues and Solutions

1. PVC Pending

   # Check PVC status
   kubectl describe pvc pvc-name
   
   # Check available PVs
   kubectl get pv
   

2. Volume Mount Failures

   # Check pod events
   kubectl describe pod pod-name
   
   # Check pod logs
   kubectl logs pod-name
   

3. Storage Class Issues

   # Verify storage class exists
   kubectl get storageclass
   
   # Check storage class details
   kubectl describe storageclass class-name
   

Next Steps

1. Implement backup solutions
2. Set up monitoring for storage usage
3. Implement dynamic provisioning
4. Study advanced storage patterns
5. Explore cloud-specific storage options