# Resizing Persistent Volume Claim in Kubernetes Cluster

When you require additional storage for your application, you may need to resize a Persistent Volume Claim (PVC) in the Kubernetes cluster. This document provides step-by-step instructions to resize a PVC in a Kubernetes cluster.

## **Prerequisites**

* Your PVC's StorageClass has to support volume expansion. Verify that your StorgeClass has `allowVolumeExpansion: true`
* Ensure you have the necessary permissions to edit PVCs and resize volumes.

## Resizing a PVC

There may be downtime when resizing a PVC in Kubernetes, especially when transferring data or resizing file systems. To securely resize a PVC, turn off the related service and follow the instructions below.

1. Identify the PVC you want to resize. Run the below command.

   ```bash
   kubectl get pvc -n <namespace>
   ```
2. Identify the pods that are using this PVC.

   ```bash
   kubectl get pods -n <namespace> --field-selector=spec.volumes.persistentVolumeClaim.claimName=<pvc-name>
   ```

   You must end the running application in order to safely resize the PVC. If the PVC is attached to a Deployment, StatefulSet, or another workload, scale it down to zero replicas.\
   **For a Deployment**

   ```bash
   kubectl scale deployment <deployment_name> --replicas=0 -n <namespace>
   ```

   **For a StatefulSet**

   ```bash
   kubectl scale statefulset <statefulset_name> --replicas=0 -n <namespace>
   ```
3. Confirm that the pods have been scaled down.

   ```bash
   kubectl get pods -n <namespace>
   ```
4. Edit the PVC to update the `spec.resources.requests.storage` field with the new size. Run the following command.

   ```bash
   kubectl edit pvc <pvc-name> -n <namespace>
   ```
5. Edit the storage field to Increase the storage size. For example, change 10GB to 20GB.

   ```yaml
   resources:
     requests:
       storage: 10Gi
   ```
6. After updating the PVC, check the status to ensure the resize operation succeeds.

   ```shell
   kubectl get pvc <pvc-name> -n <namespace>
   ```
7. After resizing the PVC and verifying that everything is in order, scale the deployment or stateful set back to its initial number of replicas.\
   **For a Deployment**

   ```
   kubectl scale deployment <deployment-name> --replicas=<desired-count> -n <namespace>
   ```

   **For a StatefulSet**

   ```
   kubectl scale statefulset <statefulset-name> --replicas=<desired-count> -n <namespace>
   ```
8. Verify that the pods are running

   ```
   kubectl get pods -n <namespace>
   ```

Note:

You can use the Rancher UI to resize the PVC by following the procedures listed above.


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