Expanding a pod volume

To expand a volume:

1. Enable volume expansion.
2. Create a PersistentVolumeClaim.
3. Create a pod with a dynamically provisioned volume.
4. Delete the pod with the volume.
5. Request volume expansion.
6. Delete the pod with the volume.

Before you start, install kubectl and configure it to work with the created Managed Service for Kubernetes cluster.

Enable volume expansionEnable volume expansion

To enable the volume expansion feature, make sure the storage class (StorageClass) description contains the allowVolumeExpansion: true parameter. In Managed Service for Kubernetes storage, this feature is enabled by default:

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: yc-network-hdd
provisioner: disk-csi-driver.mks.ycloud.io
volumeBindingMode: WaitForFirstConsumer
parameters:
  type: network-hdd
  csi.storage.k8s.io/fstype: ext4
allowVolumeExpansion: true
reclaimPolicy: Delete

Create a objectCreate a PersistentVolumeClaimobject

1. Save the following PersistentVolumeClaim creation specification to a YAML file named pvc-expansion.yaml.

   To learn more about the PersistentVolumeClaim creation specification, see the Kubernetes documentation.

   apiVersion: v1
   kind: PersistentVolumeClaim
   metadata:
     name: pvc-expansion
   spec:
     accessModes:
       - ReadWriteOnce
     storageClassName: yc-network-hdd
     resources:
       requests:
         storage: 1Gi
   

2. Create the PersistentVolumeClaim object:

   kubectl create -f pvc-expansion.yaml
   

   Result:

   persistentvolumeclaim/pvc-expansion created
   

Create a pod with a dynamically provisioned volumeCreate a pod with a dynamically provisioned volume

1. Save the following pod creation specification to a YAML file named pod.yaml.

   To learn more about the pod creation specification, see the Kubernetes documentation.

   apiVersion: v1
   kind: Pod
   metadata:
     name: pod
   spec:
     containers:
     - name: app
       image: ubuntu
       command: ["/bin/sh"]
       args: ["-c", "while true; do echo $(date -u) >> /data/out.txt; sleep 5; done"]
       volumeMounts:
       - name: persistent-storage
         mountPath: /data
     volumes:
     - name: persistent-storage
       persistentVolumeClaim:
         claimName: pvc-expansion
   

2. Create a pod:

   kubectl create -f pod.yaml
   

   Result:

   pod/pod created
   

Delete the pod with the volumeDelete the pod with the volume

To request volume expansion, you need to delete the pod.

1. Delete the pod:

   kubectl delete pod pod
   

   Result:

   pod "pod" deleted
   

Request volume expansionRequest volume expansion

Edit the spec.resources.requests.storage field of the PersistentVolumeClaim object.

1. Open the YAML file named pvc-expansion.yaml:

   kubectl edit pvc pvc-expansion
   

   In the text editor, change the disk size value and save it:

   # Please edit the object below. Lines beginning with a '#' will be ignored,
   # and an empty file will abort the edit. If an error occurs while saving this file will be
   # reopened with the relevant failures.
   #
   apiVersion: v1
   kind: PersistentVolumeClaim
   metadata:
   ...
   spec:
     accessModes:
     - ReadWriteOnce
     resources:
       requests:
        storage: 1Gi # Change to 2Gi.
   ...
   status:
     accessModes:
     - ReadWriteOnce
     capacity:
       storage: 1Gi
   phase: Bound
   

2. Wait for the volume to expand. Check the change results:

   kubectl get pvc pvc-expansion -o yaml
   

   The spec.resources.requests.storage field shows the requested volume size:

   apiVersion: v1
   kind: PersistentVolumeClaim
   metadata:
   ...
   spec:
     accessModes:
     - ReadWriteOnce
     resources:
       requests:
         storage: 2Gi
   ...
   status:
     accessModes:
     - ReadWriteOnce
     capacity:
       storage: 1Gi
   ...
   

Create a pod with a volumeCreate a pod with a volume

1. To resize the volume, create a pod:

   kubectl create -f pod.yaml
   

   Result:

   pod/pod created
   

2. Check the change results:

   kubectl get pvc pvc-expansion -o yaml
   

   The volume size increased. The status.capacity.storage field now shows the expanded size:

   apiVersion: v1
   kind: PersistentVolumeClaim
   metadata:
   ...
   spec:
     accessModes:
     - ReadWriteOnce
     resources:
       requests:
         storage: 2Gi
   ...
   status:
     accessModes:
     - ReadWriteOnce
     capacity:
       storage: 2Gi
   ...