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resizing-persistent-volume-claim-in-kubernetes-cluster.md

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Guide on Resizing PVC (Persistent Volume Claim) in Kubernetes Cluster
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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.

    kubectl get pvc -n <namespace>

  2. Identify the pods that are using this PVC.

    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

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

    For a StatefulSet

    kubectl scale statefulset <statefulset_name> --replicas=0 -n <namespace>

  3. Confirm that the pods have been scaled down.

    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.

    kubectl edit pvc <pvc-name> -n <namespace>

  5. Edit the storage field to Increase the storage size. For example, change 10GB to 20GB.

    resources:
  requests:
    storage: 10Gi

  6. After updating the PVC, check the status to ensure the resize operation succeeds.

    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.