Create Persistent Volumes with Storage Classes ¶

This topic explains how to use dynamic storage in workload clusters.

Overview: PersistentVolume, PersistentVolumeClaim, and StorageClass ¶

Within a Kubernetes cluster, PersistentVolume (PV) objects provide shared storage for cluster pods that is unaffected by pod lifecycles. Storage is provisioned to the PV through a PersistentVolumeClaim (PVC) object, which defines how much and how the pod accesses the underlying storage. For more information, see Persistent Volumes in the Kubernetes documentation.

Cluster administrators can define StorageClass objects that let cluster users dynamically create PVC and PV objects with different storage types and rules. Tanzu also provides default StorageClass objects that let users provision persistent storage in a turnkey environment.

StorageClass objects include a provisioner field identifying the internal or external service plug-in that provisions PVs, and a parameters field that associates the Kubernetes storage class with storage options defined at the infrastructure level, such as VM Storage Policies in vSphere. For more information, see Storage Classes in the Kubernetes documentation.

Supported Storage Types ¶

Tanzu Community Edition supports StorageClass objects for different storage types, provisioned by Kubernetes internal (“in-tree”) or external (“out-of-tree”) plug-ins.

Storage Types ¶

• vSphere Cloud Native Storage (CNS)
• Amazon EBS
• Azure Disk
• iSCSI
• NFS

See Default Storage Classes below for vSphere CNS, Azure EBS, and Azure Disk default storage classes.

Plug-in Locations ¶

• Kubernetes internal (“in-tree”) storage. - Ships with core Kubernetes; provider values are prefixed with kubernetes.io, e.g. kubernetes.io/aws-ebs.
• External (“out-of-tree”) storage. - Can be anywhere defined by provider value, e.g. csi.vsphere.vmware.com. - Follow the Container Storage Interface (CSI) standard for external storage.

Default Storage Classes ¶

Tanzu provides default StorageClass objects that let workload cluster users provision persistent storage on their infrastructure in a turnkey environment, without needing StorageClass objects created by a cluster administrator.

The ENABLE_DEFAULT_STORAGE_CLASS variable is set to true by default in the cluster configuration file passed to --file option of tanzu cluster create, to enable the default storage class for a workload cluster.

The Tanzu default storage class definitions are:

vSphere CNS ¶

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: default
  annotations:
    storageclass.kubernetes.io/is-default-class: "true"
provisioner: csi.vsphere.vmware.com
parameters:
  storagePolicyName: optional

See the vSphere CSI storage class parameters in the Kubernetes documentation.

Amazon EBS ¶

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: default
  annotations:
    storageclass.kubernetes.io/is-default-class: "true"
provisioner: kubernetes.io/aws-ebs

See the Amazon EBS storage class parameters in the Kubernetes documentation.

Azure Disk ¶

apiVersion: storage.k8s.io/v1beta1
kind: StorageClass
metadata:
  name: default
  annotations:
    storageclass.beta.kubernetes.io/is-default-class: "true"
  labels:
    kubernetes.io/cluster-service: "true"
provisioner: kubernetes.io/azure-disk
parameters:
  kind: Managed
  storageaccounttype: Standard_LRS
  cachingmode: ReadOnly
volumeBindingMode: WaitForFirstConsumer

See the Azure Disk storage class parameters in the Kubernetes documentation.

Create a Custom Storage Class ¶

Cluster administrators can create a new storage class as follows:

Before You Begin:

(vSphere only) Select or create the VM storage policy to use as the basis for the Kubernetes StorageClass. vSphere administrators can create a storage policy by following the steps in Set Up vSphere CNS and Create a Storage Policy in vSphere.

1. Create a StorageClass configuration .yaml with provisioner, parameters, and other options.
2. (vSphere only) Associate a Kubernetes storage class with a vSphere storage policy by setting its storagePolicyName parameter to the vSphere storage policy name, as a double-quoted string.
3. Pass the file to kubectl create -f
4. Verify the storage class by running kubectl describe storageclass <storageclass metadata.name>.

For example, see Enabling Dynamic Provisioning in the Kubernetes documentation.

For vSphere CSI information and resources, see VMware vSphere Container Storage Plug-in Documentation.

Use a Custom Storage Class in a Cluster ¶

To provision persistent storage for their cluster nodes that does not use one of the Default Storage Classes described above, cluster users include a custom storage class in a pod configuration as follows:

1. Set the context of kubectl to the cluster. For example:

   kubectl config use-context my-cluster-admin@my-cluster
   

2. Select or create a storage class.

   • Select:
     • To list available storage classes, run kubectl get storageclass.
   • Create
     • Cluster admins can create storage classes by following Create a Custom Storage Class, above.

3. Create a PVC and its PV:

   1. Create a PersistentVolumeClaim configuration .yaml with spec.storageClassName set to the metadata.name value of your StorageClass object. For an example, see Enabling Dynamic Provisioning in the Kubernetes documentation.
   2. Pass the file to kubectl create -f
   3. Run kubectl describe pvc <pvc metadata.name> to verify the PVC.
   4. A PV is automatically created with the PVC. Record its name, listed in the kubectl describe pvd output after Successfully provisioned volume.
   5. Run kubectl describe pv <pv unique name> to verify the PV.

4. Create a pod using the PVC:

   1. Create a Pod configuration .yaml that sets spec.volumes to include your PVC under persistentVolumeClaim.claimName. For an example, see Dynamic Provisioning and StorageClass API in the vSphere Storage for Kubernetes documentation.
   2. Pass the file to kubectl create -f
   3. Run kubectl get pod <pod metadata.name> to verify the pod.