Persistent Volume Expansion in Kubernetes (CloudPE)-Kubernetes

---

1. Executive Summary

Kubernetes supports in-place volume expansion, allowing you to increase the size of an existing Persistent Volume without data loss.

• The block storage is expanded at the infrastructure layer (CloudPE).
• The filesystem is then resized to utilize the new capacity.
• ✅ Existing data remains intact — no deletion, movement, or modification occurs.

---

2. Prerequisites

Before starting the expansion process, ensure the following:

🔧 Storage Configuration

The StorageClass must have:

allowVolumeExpansion: true

📈 Expansion Direction

• Only volume expansion is supported
  • Example: 5Gi → 10Gi ✅
  • Shrinking volumes ❌ (not supported and will fail validation)

🚀 Driver Status

• Ensure the CSI driver is running:

kubectl get pods -n kube-system | grep cinder

• All cinder.csi.openstack.org pods should be in Running state

---

3. Expansion Procedure (Declarative Method)

This method follows Infrastructure as Code (IaC) best practices using YAML manifests.

---

🔹 Phase A: Update the PVC Request

1. Open your PersistentVolumeClaim file (e.g., pvc.yaml)
2. Update the storage size:

spec:
  resources:
    requests:
      storage: 10Gi  # Updated from 5Gi

3. Apply the changes:

kubectl apply -f pvc.yaml

---

🔹 Phase B: Resize the Filesystem

After expanding the volume, the filesystem must be resized.

⚠️ In this environment (ext4/xfs), this requires a pod restart

If using a Deployment:

kubectl rollout restart deployment <deployment-name>

If using a Standalone Pod:

kubectl apply -f pod.yml

Kubernetes will:

• Re-attach the expanded volume
• Automatically grow the filesystem during mount

---

4. Post-Expansion Validation

Verify that the expansion was successful:

✅ Check PVC Status

kubectl get pvc <pvc-name>

• Status should be Bound
• New size should be reflected

✅ Verify Inside the Pod

kubectl exec <pod-name> -- df -h /data

• Confirm the updated storage size in the Size column

---

5. Safety & Recovery

🔒 Data Integrity

• Expansion occurs at the end of the partition
• Existing data remains untouched and safe

⚠️ Failure Handling

• If expansion fails (e.g., insufficient quota):
  • PVC status will remain: Expanding
  • Pod continues operating with the original size
• Once the issue is resolved, expansion resumes automatically

🕒 Best Practice

• Perform volume expansion during low-traffic periods
• This minimizes impact from required pod restarts

---

✅ Summary

• Safe, in-place volume expansion is supported
• Requires:
  • StorageClass configuration
  • YAML update
  • Pod restart
• Always validate after expansion

---