Chapter 7. Dynamic provisioning 7.1. About dynamic provisioning The StorageClass resource object describes and classifies storage that can be requested, as well as provides a means for passing parameters for dynamically provisioned storage on demand. StorageClass objects can also serve as a management mechanism for controlling different levels of storage and access to the storage. Cluster Administrators ( cluster-admin ) or Storage Administrators ( storage-admin ) define and create the StorageClass objects that users can request without needing any detailed knowledge about the underlying storage volume sources. The Red Hat OpenShift Service on AWS persistent volume framework enables this functionality and allows administrators to provision a cluster with persistent storage. The framework also gives users a way to request those resources without having any knowledge of the underlying infrastructure. Many storage types are available for use as persistent volumes in Red Hat OpenShift Service on AWS. While all of them can be statically provisioned by an administrator, some types of storage are created dynamically using the built-in provider and plugin APIs. 7.2. Available dynamic provisioning plugins Red Hat OpenShift Service on AWS provides the following provisioner plugins, which have generic implementations for dynamic provisioning that use the cluster's configured provider's API to create new storage resources: Storage type Provisioner plugin name Notes Amazon Elastic Block Store (Amazon EBS) kubernetes.io/aws-ebs For dynamic provisioning when using multiple clusters in different zones, tag each node with Key=kubernetes.io/cluster/<cluster_name>,Value=<cluster_id> where <cluster_name> and <cluster_id> are unique per cluster. Important Any chosen provisioner plugin also requires configuration for the relevant cloud, host, or third-party provider as per the relevant documentation. 7.3. Defining a storage class StorageClass objects are currently a globally scoped object and must be created by cluster-admin or storage-admin users. Important The Cluster Storage Operator installs a default storage class. This storage class is owned and controlled by the Operator. It cannot be deleted or modified beyond defining annotations and labels. If different behavior is desired, you must define a custom storage class. The following sections describe the basic definition for a StorageClass object and specific examples for each of the supported plugin types. 7.3.1. Basic StorageClass object definition The following resource shows the parameters and default values that you use to configure a storage class. This example uses the AWS ElasticBlockStore (EBS) object definition. Sample StorageClass definition kind: StorageClass 1 apiVersion: storage.k8s.io/v1 2 metadata: name: <storage-class-name> 3 annotations: 4 storageclass.kubernetes.io/is-default-class: 'true' ... provisioner: kubernetes.io/aws-ebs 5 parameters: 6 type: gp3 ... 1 (required) The API object type. 2 (required) The current apiVersion. 3 (required) The name of the storage class. 4 (optional) Annotations for the storage class. 5 (required) The type of provisioner associated with this storage class. 6 (optional) The parameters required for the specific provisioner, this will change from plug-in to plug-in. 7.3.2. Storage class annotations To set a storage class as the cluster-wide default, add the following annotation to your storage class metadata: storageclass.kubernetes.io/is-default-class: "true" For example: apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: annotations: storageclass.kubernetes.io/is-default-class: "true" ... This enables any persistent volume claim (PVC) that does not specify a specific storage class to automatically be provisioned through the default storage class. However, your cluster can have more than one storage class, but only one of them can be the default storage class. Note The beta annotation storageclass.beta.kubernetes.io/is-default-class is still working; however, it will be removed in a future release. To set a storage class description, add the following annotation to your storage class metadata: kubernetes.io/description: My Storage Class Description For example: apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: annotations: kubernetes.io/description: My Storage Class Description ... 7.3.3. AWS Elastic Block Store (EBS) object definition aws-ebs-storageclass.yaml kind: StorageClass apiVersion: storage.k8s.io/v1 metadata: name: <storage-class-name> 1 provisioner: kubernetes.io/aws-ebs parameters: type: io1 2 iopsPerGB: "10" 3 encrypted: "true" 4 kmsKeyId: keyvalue 5 fsType: ext4 6 1 (required) Name of the storage class. The persistent volume claim uses this storage class for provisioning the associated persistent volumes. 2 (required) Select from io1 , gp3 , sc1 , st1 . The default is gp3 . See the AWS documentation for valid Amazon Resource Name (ARN) values. 3 Optional: Only for io1 volumes. I/O operations per second per GiB. The AWS volume plugin multiplies this with the size of the requested volume to compute IOPS of the volume. The value cap is 20,000 IOPS, which is the maximum supported by AWS. See the AWS documentation for further details. 4 Optional: Denotes whether to encrypt the EBS volume. Valid values are true or false . 5 Optional: The full ARN of the key to use when encrypting the volume. If none is supplied, but encypted is set to true , then AWS generates a key. See the AWS documentation for a valid ARN value. 6 Optional: File system that is created on dynamically provisioned volumes. This value is copied to the fsType field of dynamically provisioned persistent volumes and the file system is created when the volume is mounted for the first time. The default value is ext4 . 7.4. Changing the default storage class Use the following procedure to change the default storage class. For example, if you have two defined storage classes, gp3 and standard , and you want to change the default storage class from gp3 to standard . Prerequisites Access to the cluster with cluster-admin privileges. Procedure To change the default storage class: List the storage classes: USD oc get storageclass Example output NAME TYPE gp3 (default) kubernetes.io/aws-ebs 1 standard kubernetes.io/aws-ebs 1 (default) indicates the default storage class. Make the desired storage class the default. For the desired storage class, set the storageclass.kubernetes.io/is-default-class annotation to true by running the following command: USD oc patch storageclass standard -p '{"metadata": {"annotations": {"storageclass.kubernetes.io/is-default-class": "true"}}}' Note You can have multiple default storage classes for a short time. However, you should ensure that only one default storage class exists eventually. With multiple default storage classes present, any persistent volume claim (PVC) requesting the default storage class ( pvc.spec.storageClassName =nil) gets the most recently created default storage class, regardless of the default status of that storage class, and the administrator receives an alert in the alerts dashboard that there are multiple default storage classes, MultipleDefaultStorageClasses . Remove the default storage class setting from the old default storage class. For the old default storage class, change the value of the storageclass.kubernetes.io/is-default-class annotation to false by running the following command: USD oc patch storageclass gp3 -p '{"metadata": {"annotations": {"storageclass.kubernetes.io/is-default-class": "false"}}}' Verify the changes: USD oc get storageclass Example output NAME TYPE gp3 kubernetes.io/aws-ebs standard (default) kubernetes.io/aws-ebs

Commands:
kind: StorageClass 1 apiVersion: storage.k8s.io/v1 2 metadata: name: <storage-class-name> 3 annotations: 4 storageclass.kubernetes.io/is-default-class: 'true' provisioner: kubernetes.io/aws-ebs 5 parameters: 6 type: gp3
storageclass.kubernetes.io/is-default-class: "true"
apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: annotations: storageclass.kubernetes.io/is-default-class: "true"
kubernetes.io/description: My Storage Class Description
apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: annotations: kubernetes.io/description: My Storage Class Description
kind: StorageClass apiVersion: storage.k8s.io/v1 metadata: name: <storage-class-name> 1 provisioner: kubernetes.io/aws-ebs parameters: type: io1 2 iopsPerGB: "10" 3 encrypted: "true" 4 kmsKeyId: keyvalue 5 fsType: ext4 6
oc get storageclass
NAME TYPE gp3 (default) kubernetes.io/aws-ebs 1 standard kubernetes.io/aws-ebs
oc patch storageclass standard -p '{"metadata": {"annotations": {"storageclass.kubernetes.io/is-default-class": "true"}}}'
oc patch storageclass gp3 -p '{"metadata": {"annotations": {"storageclass.kubernetes.io/is-default-class": "false"}}}'
oc get storageclass
NAME TYPE gp3 kubernetes.io/aws-ebs standard (default) kubernetes.io/aws-ebs