Overview of persistent storage for CKS clusters - ScitiX

CKS clusters use Kubernetes persistent volumes to store workload data. If training data, model files, or task output must be retained after Pods are rebuilt, first prepare persistent storage, then use a PVC to mount the storage to the workload.

Learn about persistent storage objects

Object	Description	Scope
PV (PersistentVolume)	Represents a piece of persistent storage available for use by a cluster. A PV includes information such as capacity, access modes, reclaim policy, and storage backend.	Cluster level
PVC (PersistentVolumeClaim)	Represents a workload’s request for storage capacity and Access Method. Workloads use PVs through PVCs rather than referencing PVs directly.	Namespace level
StorageClass	Defines how storage volumes are dynamically created, including the storage plugin, reclaim policy, and storage parameters.	Cluster level

After a PVC is bound to an eligible PV, its status changes to Bound. A workload can reference only PVCs in the same namespace.

Select how to use a storage volume

Depending on whether the backend storage is ready, choose a dynamic storage volume or a static storage volume.

Method	Applicable scenario	Resource relationship	Required preparations
Dynamic volumes	You want PVs to be created automatically based on PVC requests.	StorageClass → PVC → Automatically created PV	An available storage plugin and StorageClass. When using GPFS, you can also create a StorageClass through a volume template.
Static volumes	The backend storage already exists, or storage resources need to be prepared in advance by a storage administrator.	Backend storage → Manually created PV → PVC	Backend storage information and a PV configuration that matches the storage.

StorageClass is the core object for dynamically provisioning storage volumes. When using static storage volumes, you can also match PVs and PVCs through storageClassName, but StorageClass will not automatically create PVs.

Using persistent storage

Depending on how the Volume is prepared, create or bind a storage volume:
- Use Dynamic Persistent Volumes
- Use Static Persistent Volumes
Verify that the PVC status is Bound.
Mount persistent storage to a workload.
When you no longer need the storage resources, clean up persistent storage resources.