When deploying applications on OpenShift, storage plays a crucial role in ensuring that data is preserved and accessible beyond the lifespan of individual containers. Unlike stateless applications, many workloads require persistent storage—databases, message queues, and file-based systems all rely on data that must survive restarts and scaling events.
What is OpenShift Storage?
OpenShift storage provides a framework for managing persistent data in a Kubernetes-based environment. It uses Persistent Volumes (PVs) and Persistent Volume Claims (PVCs) to abstract the underlying storage infrastructure. This allows developers to request storage without worrying about the specifics of the backend.
OpenShift supports multiple storage backends, including:
- Block storage – Ideal for databases and applications needing low-latency, high-performance storage.
- File storage – Shared storage that can be mounted by multiple pods simultaneously.
- Object storage – Storage for unstructured data like images, backups, and archives.
Key Concepts
Persistent Volumes (PV)
A Persistent Volume represents a piece of storage in the cluster provisioned by an administrator or dynamically by a StorageClass.
Persistent Volume Claims (PVC)
A PVC is a request for storage by a user. OpenShift binds the PVC to an available PV that meets the requested size and access mode.
StorageClasses
StorageClasses define different storage “profiles” (e.g., fast SSD, high-capacity HDD). When a PVC is created with a StorageClass, OpenShift can dynamically provision storage that matches the requested profile.
Container Storage Interface (CSI)
The Container Storage Interface (CSI) is a Kubernetes standard for exposing arbitrary storage systems to containerized workloads. OpenShift fully adopts the CSI model because it provides a consistent, extensible way to integrate with a wide range of storage providers. By using CSI, Red Hat ensures that OpenShift can support both on-premises and cloud-based storage solutions without requiring proprietary plugins.
Red Hat chooses CSI because:
- It is a vendor-neutral standard supported by the Kubernetes community.
- It simplifies storage driver development and maintenance.
- It enables faster adoption of new storage technologies without core platform changes.
- It ensures portability across hybrid and multi-cloud environments.
Why is Storage Important in OpenShift?
Containers are ephemeral by design, meaning that once a container stops, its file system is lost. Persistent storage enables applications to retain state, making it possible to run databases, content management systems, and other stateful workloads in OpenShift.
Common Use Cases
- Running databases (MySQL, PostgreSQL, MongoDB)
- Hosting file-based applications (WordPress, Drupal)
- Storing logs, backups, and artifacts
- Supporting AI/ML workloads requiring large datasets
Next Steps
To get started with OpenShift storage:
- Learn about the different storage backends supported by your cluster.
- Explore how to create and manage Persistent Volume Claims.
- Experiment with StorageClasses for dynamic provisioning.
In future posts, we will dive deeper into setting up specific storage solutions and best practices for running stateful applications on OpenShift.