Storage Class

Storage Class in Kubernetes¶

A StorageClass defines how storage should be provisioned dynamically. It provides a way to dynamically provision PVs. Defines how PVs are created on-demand.

Key Characteristics:¶

Provisioner: The component that creates the PV (e.g., AWS EBS, GCE PD, etc.).
Tells Kubernetes what provisioner to use (e.g., AWS EBS, NFS, hostPath, etc).
Defines reclaim policies (Delete, Retain, Recycle).
Used by PVC to dynamically provision PV.

StorageClass Example for AWS EBS¶

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: ebs-sc # Name of the storage class (usually dynamic provisioner)
provisioner: kubernetes.io/aws-ebs  # Defines which external provisioner to use
parameters:
  type: gp2  # General purpose SSD
  fsType: ext4  # Filesystem type
reclaimPolicy: Delete  # Automatically delete volume when PVC is deleted
volumeBindingMode: WaitForFirstConsumer  # Delay volume binding until pod is scheduled

StorageClass Example for NFS¶

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: nfs
provisioner: nfs.csi.k8s.io
parameters:
  server: nfs-server.example.com
  share: /exported/path
mountOptions:
  - vers=4.1
reclaimPolicy: Retain
volumeBindingMode: Immediate

StorageClass Example for CSI (EBS CSI Driver)¶

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: csi-sc
provisioner: ebs.csi.aws.com
parameters:
  type: gp2
  fsType: ext4
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer

PVC Using StorageClass¶

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: ebs-pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi
  storageClassName: ebs-sc  # Links to the above StorageClass # This will trigger dynamic provisioning

The StorageClass must be created before the PVC. The PVC will then use the StorageClass to dynamically provision a PV.

⏳ As soon as this PVC is applied, Kubernetes will automatically provision an EBS volume, create a matching PV, and bind it to this PVC.

Exactly, sweetheart — you're 💯 right.

When your StorageClass uses:

provisioner: kubernetes.io/no-provisioner

then:

✅ YOU must create the PersistentVolume manually — otherwise your PersistentVolumeClaim stays Pending.

🔁 Here's the logic:¶

Component	What it Does	Notes
`StorageClass`	Tells Kubernetes how to provision storage	If `no-provisioner`, no automatic volume will be created.
`PersistentVolume`	Actual storage resource in the cluster	You must create this manually if using `no-provisioner`.
`PersistentVolumeClaim`	A request for storage from the app	Binds only when a matching `PV` exists.

✅ If you're using a CSI provisioner (like AWS EBS, GCE PD, or hostpath provisioner):¶

Then the provisioner will automatically create PVs. Example:

provisioner: hostpath.csi.k8s.io

But with kubernetes.io/no-provisioner, you are saying: “I will manage the PVs myself.”

✅ Summary¶

Yes, even if you create a StorageClass, you still must create a PersistentVolume manually when using no-provisioner.
PVC only binds to PV — StorageClass helps PVC select the right PV.