Persisting Data in Kubernetes Using Volumes

Overview

• Kubernetes does not provide data persistence out-of-the-box.
• To ensure data persistence, you must explicitly configure storage that is independent of the pod lifecycle.
• Storage must be available on all nodes and highly available to survive cluster crashes.
• Use cases for persistent storage include databases and directories for files.

Key Components of Kubernetes Storage

Persistent Volume (PV)

• A cluster resource used to store data.
• Defined in a YAML file specifying the storage amount and storage backend.
• Abstracts the actual physical storage (local disk, NFS server, cloud storage).
• Not namespace-scoped, accessible to the whole cluster.
• Admins create PVs.

Persistent Volume Claim (PVC)

• Allows applications to claim storage from a PV.
• Defined with YAML specifying storage size and access type.
• Must exist in the same namespace as the pod using it.

Storage Class

• Automates PV provisioning dynamically using a storage class defined in YAML.
• Defines the storage backend using a provisioner attribute.
• Used by PVC to request storage provisioning.

Use Cases and Best Practices

Database Persistence

• Requires remote storage to ensure storage is node-independent and survives cluster crashes.
• Persistent storage types are essential for data reliability.

Local vs. Remote Volumes

• Local volumes violate node independence and crash resilience requirements.
• Remote storage should be used for data needing high availability.

Configuration Files and Certificates

• Use ConfigMap and Secret for local volumes needed for configuration files and certificates.
• These are managed by Kubernetes itself and not through PV/PVC.

Abstractions and Roles

• Admins set up actual storage and create PVs based on developer needs.
• Developers use PVCs to claim storage for applications.
• Abstractions like Storage Class simplify storage requests and management.

Practical Considerations

• Multiple storage types can be used simultaneously within a pod.
• Pods specify volumes to provide in volumes attribute and use volumeMounts attribute to access storage in containers.
• Storage Class simplifies handling storage needs in clusters with frequent deployments.

Additional Resources

• Kubernetes documentation for a complete list of supported storage backends.
• Upcoming videos will cover specific volume types and detailed examples.

Conclusion

• Understanding and utilizing Kubernetes storage components is critical for ensuring data persistence and application reliability.
• Future videos will delve deeper into practical applications and configurations.