Expanding a volume

To expand a volume, follow these steps.

Enable volume expansion

To enable the volume expansion feature, make sure the storage class (StorageClass) description contains allowVolumeExpansion: true. 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 PersistentVolumeClaim

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 a PersistentVolumeClaim:

   kubectl create -f pvc-expansion.yaml
   

   Command execution result:

   persistentvolumeclaim/pvc-expansion created
   

Create 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
   

   Command execution result:

   pod/pod created
   

Delete the pod with the volume

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

1. Delete the pod:

   kubectl delete pod pod
   

   Command execution result:

   pod "pod" deleted
   

Request volume expansion

Make changes to the spec.resources.requests.storage field of the PersistentVolumeClaim.

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 the value 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 volume

1. To resize the volume, create a pod:

   kubectl create -f pod.yaml
   

   Command execution 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 shows the expanded size:

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