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Kubernetes Storage Workshop: RWO and RWX with PV and PVC

This workshop demonstrates the use of PersistentVolumes (PVs) and PersistentVolumeClaims (PVCs) in Kubernetes with ReadWriteOnce (RWO) and ReadWriteMany (RWX) access modes. Minikube's default storage provisioner is used for dynamic volume provisioning.

1. Prerequisites

  • Minikube is installed and running: 
    minikube start
  • Enable the default storage provisioner: 
    minikube addons enable storage-provisioner

2. Example: ReadWriteOnce (RWO)

Step 1: Create PersistentVolume and PVC

pv-rwo.yaml:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc-rwo
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi

Apply the manifest:

kubectl apply -f pv-rwo.yaml

Verify that the resources were created:

kubectl get pv
kubectl get pvc

Step 2: Create Pod1 Using the PVC

pod1-rwo.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: pod1-rwo
spec:
  containers:
  - name: busybox
    image: busybox
    command: ["sleep", "3600"]
    volumeMounts:
    - mountPath: "/data"
      name: storage
  volumes:
  - name: storage
    persistentVolumeClaim:
      claimName: pvc-rwo

Apply the manifest:

kubectl apply -f pod1-rwo.yaml

Verify the Pod is running:

kubectl get pods

Step 3: Attempt to Create Pod2 Using the Same PVC

pod2-rwo.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: pod2-rwo
spec:
  containers:
  - name: busybox
    image: busybox
    command: ["sleep", "3600"]
    volumeMounts:
    - mountPath: "/data"
      name: storage
  volumes:
  - name: storage
    persistentVolumeClaim:
      claimName: pvc-rwo

Apply the manifest:

kubectl apply -f pod2-rwo.yaml

Step 4: Test Storage

  1. Access Pod1: 
    kubectl exec -it pod1-rwo -- sh
  2. Write data to the volume: 
    echo "RWO Test Data" > /data/testfile.txt
  3. Exit the Pod: 
    exit
  4. Access Pod1: 
    kubectl exec -it pod2-rwo -- sh
  5. Write data to the volume: 
    ls /data/testfile.txt
  6. Exit the Pod: 
    exit

3. Example: ReadWriteMany (RWX)

Step 1: Create PersistentVolume and PVC

pv-rwx.yaml:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-rwx
spec:
  capacity:
    storage: 1Gi
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Retain
  hostPath:
    path: /data/rwx
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc-rwx
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 1Gi
  volumeName: pv-rwx

Apply the manifest:

kubectl apply -f pv-rwx.yaml

Verify that the resources were created:

kubectl get pv
kubectl get pvc

Step 2: Create Two Pods Using the Same PVC

pod1-rwx.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: pod1-rwx
spec:
  containers:
  - name: busybox
    image: busybox
    command: ["sleep", "3600"]
    volumeMounts:
    - mountPath: "/data"
      name: shared-storage
  volumes:
  - name: shared-storage
    persistentVolumeClaim:
      claimName: pvc-rwx

pod2-rwx.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: pod2-rwx
spec:
  containers:
  - name: busybox
    image: busybox
    command: ["sleep", "3600"]
    volumeMounts:
    - mountPath: "/data"
      name: shared-storage
  volumes:
  - name: shared-storage
    persistentVolumeClaim:
      claimName: pvc-rwx

Apply both manifests:

kubectl apply -f pod1-rwx.yaml
kubectl apply -f pod2-rwx.yaml

Verify that both Pods are running:

kubectl get pods

Step 3: Test Shared Storage

  1. Access Pod1: 
    kubectl exec -it pod1-rwx -- sh
  2. Write data to the shared volume: 
    echo "RWX Test Data" > /shared-data/testfile.txt
  3. Exit Pod1: 
    exit
  4. Access Pod2: 
    kubectl exec -it pod2-rwx -- sh
  5. Verify the data: 
    cat /shared-data/testfile.txt
    Expected output: 
    RWX Test Data

4. Cleanup

To remove all resources:

kubectl delete pod pod1-rwo pod2-rwo pod1-rwx pod2-rwx
kubectl delete pvc pvc-rwo pvc-rwx
kubectl delete pv pv-rwo pv-rwx

5. Key Takeaways

  • RWO (ReadWriteOnce): Allows one Pod to mount the volume at a time.
  • RWX (ReadWriteMany): Allows multiple Pods to share the same volume.
  • Minikube’s hostPath simplifies testing PVs and PVCs locally.