StorageClasses

StorageClass is a Kubernetes resource that describes a class of storage offered in a cluster. It defines how storage should be provisioned and managed for PersistentVolumeClaims, allowing administrators to provide dynamic, provider-specific storage without manually creating PVs.

A StorageClass includes fields such as provisioner (the driver that provisions volumes), parameters (driver-specific settings), reclaimPolicy (what happens to a PV when the PVC is released), volumeBindingMode, and allowedTopologies. The provisioner may be a cloud provider driver (for example, AWS EBS or GCE PD) or a container storage interface (CSI) driver. Some fields are optional, and features vary by driver.

Workflow: when a PVC references a StorageClass, Kubernetes calls the provisioner to create a matching PV and binds the PVC to that PV. If no StorageClass is specified but a defaultStorageClass exists, the default is used automatically. If no StorageClass is present and no default exists, dynamic provisioning may fail, and manual PV creation is required.

VolumeBindingMode controls when provisioning and binding occur (Immediate vs WaitForFirstConsumer). ReclaimPolicy determines whether the PV is deleted or retained when the PVC is deleted. AllowedTopologies constraining storage to certain nodes or zones enables multi-zone or regional storage. StorageClasses enable management of storage types across clouds and on-premises, while remaining transparent to applications.