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Persistent Volumes

Kubernetes can create volumes and mount into the containers. Any volume created by kubernetes will be visible in your Cloudify.ro account. Note: persistent volumes created by kubernetes will be billed as any other volume created from your cloud account.

Full documentation on Persistent Volumes in Kubernetes can be found here: persistent-volumes

Requirements:​

  • You have an account on Cloudify.ro *Register
  • You have created a Cloudify.ro Kubernetes Cluster *Create Cluster
  • You have downloaded the corresponding kubeconfig file and kubectl is working *Authentication

Creating Persistent Volumes with CSI Cinder Controller​

Before you can create a volume, a StorageClass must be created with Cinder as the provisioner. As usual, the K8s objects are sent to your cluster in YAML format and kubectl apply:

storageclass.yaml:

# Default NVMe class
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: csi-cinder-nvme
  annotations:
    storageclass.kubernetes.io/is-default-class: "true"
provisioner: cinder.csi.openstack.org
allowVolumeExpansion: true
parameters:
  type: NVMe
---
# Secondary HDD class
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: csi-cinder-hdd
provisioner: cinder.csi.openstack.org
allowVolumeExpansion: true
parameters:
  type: HDD

Create resource

$ kubectl apply -f storageclass.yaml

Check resource with get and describe

$ kubectl get storageclass
$ kubectl describe storageclass csi-cinder-nvme

Create a Persistent Volume Claim (PVC), you can create a new volume with the help of a Persistent Volume Claim, Persistent Volume is created dynamically by the CSI Cinder Controller.

pvc.yaml:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: nginx-pvc
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi

Create a deployment and a service​

The deployment is a nginx server for testing purposes.

deplyment.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx
        name: nginx
        ports:
        - containerPort: 80
          protocol: TCP
        volumeMounts:
          - mountPath: /usr/share/nginx/html
            name: shared
      volumes:
      - name: shared
        persistentVolumeClaim:
          claimName: nginx-pvc
          readOnly: false

---

apiVersion: v1
kind: Service
metadata:
  name: nginx-svc
spec:
  ports:
    - port: 80
      targetPort: 80
      protocol: TCP
      name: http
  selector:
    app: nginx
  type: LoadBalancer

Apply resources

$ kubectl apply -f deployment.yaml

Check resources

$ kubectl get deployments

Access nginx terminal:

$ k exec -it deployment/nginx bash

Add content to html page from nginx terminal:

$ echo "Hello world!" > /usr/share/nginx/html/index.html

Kubernetes and the CSI Cinder Controller naturally ensure that your new volume and the associated pods are always started at the same worker node.