Volumes

Every cluster ships a default StorageClass, kubrain. Declare a standard PersistentVolumeClaim and a real volume is created and attached when a pod first uses it (WaitForFirstConsumer); data survives pod restarts and reschedules.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: data
spec:
  accessModes: ["ReadWriteOnce"]
  storageClassName: kubrain
  resources:
    requests:
      storage: 20Gi

Design around ReadWriteOnce

The kubrain class is RWO — a volume attaches to one node at a time. Shape your workload accordingly:

• Single-instance stateful (a database): replicas: 1, one PVC, and deployment.strategy: Recreate in kubrain.yaml so the volume detaches cleanly before the new pod attaches.
• Multi-replica stateful: use a StatefulSet via a kubrain/k8s-templates/statefulset.yaml override with volumeClaimTemplates (one volume per replica).

Cost

Volumes bill at €0.05 / GiB-month, with the first 20 GiB free per tenant. Deleting the PVC frees the volume and stops the charge.

See also

• kubrain.yaml › Storage · Pricing.