Static Provisioning

In Volume we discussed how we can create a PV and a PVC to bind to that PV and finally configure a pod to use the PVC to get a persistent volume.

The problem with this approach is that we need to manually provision the storage on a cloud provider before we can create a PV using it. This is called as static provisioning.

Dynamic Provisioning

In dynamic provisioning, a provisioner is created which can automatically provision storage on the cloud and attach them to the pod when the claim is made. Dynamic provisioning is achieved by creating a StorageClass object.

When using storage classes, we don’t need to create PVs manually. When a PVC is created with a storage class, the storage class uses a provisioner to automatically provision storage and create a PV to bind to the PVC.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
	name: gcp-storage
provisioner: kubernetes.io/gce-pd

provisioner depends on the type of underlying storage being used (EBS, AzureDisk, etc.)

provisioner: kubernetes.io/no-provisioner means dynamic provisioning is disabled.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
	name: myclaim
spec:
	storageClassName: gcp-storage
	accessModes:
		- ReadWriteOnce
	resources:
		requests:
			storage: 500Mi

Depending on the provisioner, there are some properties that we can specify to control the behavior of the underlying storage.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
	name: gcp-storage
provisioner: kubernetes.io/gce-pd
parameters:
	type: pd-ssd
	replication-type: regional-pd

Using these properties, we can create classes of storage such as silver, gold & platinum with increasing levels of replication and speed.

Reclaim Policy and Volume Binding Mode

reclaimPolicy defines the behavior of the PV when the PVC is deleted

• Delete - delete the PV when the PVC is deleted
• Retain - retain the PV when the PVC is deleted

volumeBindingMode defines when the volume should be created and bound to a PVC

• WaitForFirstConsumer - wait for a pod to use the PVC
• Immediate - immediately create a volume and bind it to the PVC

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
	name: gcp-storage
provisioner: kubernetes.io/gce-pd
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer