Ondat Volume Guide
Follow the recipes on this page to create your first PVC (Persistent Volume Claim) using Ondat. Ondat implements dynamic provisioning, so the creation of a PVC will automatically provision a PV (PersistentVolume) that can be used to persist data written by a Pod.
Create the PersistentVolumeClaim
You can find the basic examples in the Ondat use-cases repository, in the
git clone https://github.com/storageos/use-cases.git storageos-usecases cd storageos-usecases/00-basic
apiVersion: v1 kind: PersistentVolumeClaim metadata: name: my-vol-1 spec: storageClassName: "storageos" # Ondat StorageClass accessModes: - ReadWriteOnce resources: requests: storage: 5Gi
The above PVC will dynamically provision a 5GB volume using the
storageosStorageClass. This StorageClass was created during the Ondat install and triggers creation of a PersistentVolume by Ondat.
For installations with CSI, you can create multiple StorageClasses in order to specify default labels.
apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: name: ondat-replicated provisioner: csi.storageos.com # Provisioner when using CSI parameters: csi.storage.k8s.io/fstype: ext4 storageos.com/replicas: "1" # Enforces 1 replica for the Volume csi.storage.k8s.io/secret-name: storageos-api csi.storage.k8s.io/secret-namespace: storageos
The above StorageClass has the
storageos.com/replicaslabel set. This label tells Ondat to create a volume with a replica. Adding Ondat feature labels to the StorageClass ensures all volumes created with the StorageClass have the same labels. For simplicity’s sake this example will use unreplicated volumes.
apiVersion: v1 kind: PersistentVolumeClaim metadata: name: my-vol-1 spec: storageClassName: "ondat-replicated" # Reference to the StorageClass accessModes: - ReadWriteOnce resources: requests: storage: 5Gi
You can also choose to add the label in the PVC definition rather than the StorageClass. The PVC definition takes precedence over the SC.
apiVersion: v1 kind: PersistentVolumeClaim metadata: name: my-vol-1 labels: storageos.com/replicas: "1" spec: storageClassName: "storageos" accessModes: - ReadWriteOnce resources: requests: storage: 5Gi
The above PVC has the
storageos.com/replicaslabel set. This label tells Ondat to add a replica for the volume that is created. For the sake of keeping this example simple an unreplicated volume will be used.
Move into the examples folder and create a PVC using the PVC definition above.
# from storageos-usecases/00-basic kubectl create -f ./pvc-basic.yaml
You can view the PVC that you have created with the command below
$ kubectl get pvc NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE pvc-1 Bound pvc-f8ffa027-e821-11e8-bc0b-0ac77ccc61fa 5Gi RWO storageos 1m
Create a pod that mounts the PVC created in step 2.
kubectl create -f ./pod.yaml
The command above creates a Pod that uses the PVC that was created in step 1.
apiVersion: v1 kind: Pod metadata: name: d1 spec: containers: - name: debian image: debian:9-slim command: ["/bin/sleep"] args: [ "3600" ] volumeMounts: - mountPath: /mnt name: v1 volumes: - name: v1 persistentVolumeClaim: claimName: pvc-1
In the Pod definition above volume v1 references the PVC created in step 2, and is mounted in the pod at /mnt. In this example a debian image is used for the container but any container image with a shell would work for this example.
Confirm that the pod is up and running
$ kubectl get pods NAME READY STATUS RESTARTS AGE d1 1/1 Running 0 1m
Execute a shell inside the container and write some contents to a file
$ kubectl exec -it d1 -- bash [email protected]:/# echo "Hello World!" > /mnt/helloworld [email protected]:/# cat /mnt/helloworld Hello World!
By writing to /mnt inside the container, the Ondat volume created by the PVC is being written to. If you were to kill the pod and start it again on a new node, the helloworld file would still be avaliable.
If you wish to see more use cases with actual applications, see our Use Cases documentation.