9.5. Dynamic provisioning
9.5.1. 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 intimate knowledge about the underlying storage volume sources.
The OpenShift Container Platform 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 OpenShift Container Platform. Storage plug-ins might support static provisioning, dynamic provisioning or both provisioning types.
9.5.2. Dynamic provisioning in OpenShift Data Foundation
Red Hat OpenShift Data Foundation is software-defined storage that is optimised for container environments. It runs as an operator on OpenShift Container Platform to provide highly integrated and simplified persistent storage management for containers.
OpenShift Data Foundation supports a variety of storage types, including:
- Block storage for databases
- Shared file storage for continuous integration, messaging, and data aggregation
- Object storage for archival, backup, and media storage
Version 4 uses Red Hat Ceph Storage to provide the file, block, and object storage that backs persistent volumes, and Rook.io to manage and orchestrate provisioning of persistent volumes and claims. NooBaa provides object storage, and its Multicloud Gateway allows object federation across multiple cloud environments (available as a Technology Preview).
In OpenShift Data Foundation 4, the Red Hat Ceph Storage Container Storage Interface (CSI) driver for RADOS Block Device (RBD) and Ceph File System (CephFS) handles the dynamic provisioning requests. When a PVC request comes in dynamically, the CSI driver has the following options:
-
Create a PVC with ReadWriteOnce (RWO) and ReadWriteMany (RWX) access that is based on Ceph RBDs with volume mode
Block. -
Create a PVC with ReadWriteOnce (RWO) access that is based on Ceph RBDs with volume mode
Filesystem. The supportedfstypeforFilesystemmode isext4. This is the default. -
Create a PVC with ReadWriteOnce (RWO) and ReadWriteMany (RWX) access that is based on CephFS for volume mode
Filesystem. - Create a PVC with ReadWriteOncePod (RWOP) access that is based on CephFS,NFS and RBD. With RWOP access mode, you mount the volume as read-write by a single pod on a single node.
The judgment of which driver (RBD or CephFS) to use is based on the entry in the storageclass.yaml file.
9.5.3. Available dynamic provisioning plug-ins
OpenShift Container Platform provides the following provisioner plug-ins, which have generic implementations for dynamic provisioning that use the cluster’s configured provider’s API to create new storage resources:
| Storage type | Provisioner plug-in name | Notes |
|---|---|---|
| OpenStack Cinder |
| |
| AWS Elastic Block Store (EBS) |
|
For dynamic provisioning when using multiple clusters in different zones, tag each node with |
| AWS Elastic File System (EFS) | Dynamic provisioning is accomplished through the EFS provisioner pod and not through a provisioner plug-in. | |
| Azure Disk |
| |
| Azure File |
|
The |
| GCE Persistent Disk (gcePD) |
| In multi-zone configurations, it is advisable to run one OpenShift Container Platform cluster per GCE project to avoid PVs from being created in zones where no node in the current cluster exists. |
|
| ||
| Red Hat Virtualization |
|
Any chosen provisioner plug-in also requires configuration for the relevant cloud, host, or third-party provider as per the relevant documentation.
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