How to Resize Persistent Volumes in AWS EKS Cluster

In this blog, you will learn how to resize the persistent volume in AWS EKS cluster by using a custom storage class with the allowVolumeExpansion parameter enabled.

Using Default StorageClass

In every EKS cluster, there is default Storage class with allowVolumeExpansion false. Which means you cannot update a persistent volume with the default storage class.

Lets look at the default storage class to understand more.

Run the following command to get the default storageclass name.

kubectl get sc

The name of my default storage class is given below.

As you can see in the default storage class, the allowVolumeExpansion parameter is set as false.

If we try to resize the persistence volume, which uses the default storage class, we will get the below forbidden error.

error: persistentvolumeclaims "expandable-pvc" could not be patched: persistentvolumeclaims "expandable-pvc" is forbidden: only dynamically provisioned pvc can be resized and the storageclass that provisions the pvc must support resize
You can run `kubectl replace -f /var/folders/w8/zfm6dvnj5ng6cmpv61_nydh00000gn/T/kubectl-edit-57474951.yaml` to try this update again.

Using Custom StorageClass

Let's try to expand a PVC that uses custom storageclass with allowVolumeExpansion parameter set as true.

Step 1: Create Custom StorageClass

Now, let's create a custom storage class and create the PVC with the custom storageclass.

Create a YAML file sc.yaml and copy the below manifest file content

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: expandable-sc
provisioner: kubernetes.io/aws-ebs
parameters:
  type: gp2
allowVolumeExpansion: true

You can see in the above manifest file, the allowVolumeExpansion is set as true.

The EBS volume type is set to gp2, if you want to use other volume types refer to this guide.

Let's create the PVC using the custom storageclass and try to expand the volume size.

Run the following command to create the custom storageclass

kubectl apply -f sc.yaml

Now, run the below command to check if the storageclass is created

kubectl get sc

The custom storageclass volumeBindingMode is set as Immediate, which means the PVC will be created and bound with a PV immediately after it's created.

Step 2: Create PVC

Create a manifest file pvc.yaml and copy the below PVC manifest content

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: expandable-pvc
spec:
  accessModes:
    - ReadWriteOnce
  volumeMode: Filesystem
  resources:
    requests:
      storage: 1Gi
  storageClassName: expandable-sc

You can see the storage requested is 1Gi. Run the following command to create a PVC

kubectl apply -f pvc.yaml

Run the following command to check if the PVC is created.

As you can see, the PVC is in the bound state even without being claimed by a pod because the custom storageclass we created has the volumeBindingMode as Immediate.

Step 3: Deploy a Pod

Now, create a manifest file pod.yaml and copy the below pod deployment manifest content

apiVersion: v1
kind: Pod
metadata:
  name: volume-test
spec:
  containers:
  - name: volume-test
    image: nginx
    volumeMounts:
    - name: expandable-storage
      mountPath: /data
  volumes:
  - name: expandable-storage
    persistentVolumeClaim:
      claimName: expandable-pvc

Run the following command to deploy the pod

kubectl apply -f pod.yaml

Step 4: Expand the Volume Size

Now, run the following command to edit the PVC to expand the volume size.

k edit pvc expandable-pvc

Then, change the storage request size to 2Gi as shown below

Save the changes and exit.

Wait for some time, and the PV and PVC capacity will be increased, as shown below.

Now that the volume has been increased, it's important to check if the filesystem's size inside the pod has also increased.

Run the following command to check whether the filesystem size is increased.

kubectl exec -it volume-test -- df -h /data

You can see the filesystem size has been increased as well.

Conclusion

In this blog, you have seen what happens if we change the volume size in the EKS cluster using the default storage class, which has allowVolumeExpansion parameter disabled.

Also, you have learned how to expand a volume size using a custom storage class, which has allowVolumeExpansion parameter enabled.

Also, resizing volume is one of the important topic in CKA certification.