You can provision your OpenShift cluster with storage dynamically when running in a cloud environment. The Kubernetes persistent volume framework allows administrators to provision a cluster with persistent storage and 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 OpenShift. While all of them can be statically provisioned by an administrator, some types of storage can be created dynamically using an API. These types of storage can be provisioned in an OpenShift cluster using the new and experimental dynamic storage feature.
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Dynamic provisioning of persistent volumes is currently a Technology Preview feature, introduced in OpenShift Enterprise 3.1.1. This feature is experimental and expected to change in the future as it matures and feedback is received from users. New ways to provision the cluster are planned and the means by which one accesses this feature is going to change. Backwards compatibility is not guaranteed. |
OpenShift provides the following provisioner plug-ins, which have generic implementations for dynamic provisioning that use the cluster’s configured cloud provider’s API to create new storage resources:
| Storage Type | Provisioner Plug-in Name | Required Cloud Configuration | Notes |
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OpenStack Cinder |
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AWS Elastic Block Store (EBS) |
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For dynamic provisioning when using multiple clusters in different zones, each
node must be tagged with |
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GCE Persistent Disk (gcePD) |
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In multi-zone configurations, PVs must be created in the same region/zone as
the master node. Do this by setting the
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For any chosen provisioner plug-ins, the relevant cloud configuration must also be set up, per Required Cloud Configuration in the above table. |
When your OpenShift cluster is configured for EBS, GCE, or Cinder, the associated provisioner plug-in is implied and automatically enabled. No additional OpenShift configuration by the cluster administration is required for dynamic provisioning.
For example, if your OpenShift cluster is configured to run in AWS, the EBS provisioner plug-in is automatically available for creating dynamically provisioned storage requested by a user.
Future provisioner plug-ins will include the many types of storage a single provider offers. AWS, for example, has several types of EBS volumes to offer, each with its own performance characteristics; there is also an NFS-like storage option. More provisioner plug-ins will be implemented for the supported storage types available in OpenShift.
Users can request dynamically provisioned storage by including a storage class annotation in their persistent volume claim:
kind: "PersistentVolumeClaim"
apiVersion: "v1"
metadata:
name: "claim1"
annotations:
volume.alpha.kubernetes.io/storage-class: "foo" (1)
spec:
accessModes:
- "ReadWriteOnce"
resources:
requests:
storage: "3Gi"| 1 | The value of the volume.alpha.kubernetes.io/storage-class annotation is
not meaningful at this time. The presence of the annotation, with any arbitrary
value, triggers provisioning using the single implied
provisioner plug-in per cloud. |
Volumes created dynamically by a provisioner have their
persistentVolumeReclaimPolicy set to Delete. When a persistent volume
claim is deleted, its backing persistent volume is considered released of its
claim, and that resource can be reclaimed by the cluster. Dynamic provisioning
utilizes the provider’s API to delete the volume from the provider and then
removes the persistent volume from the cluster.