Volumes and Persistent Storage¶

Object	What it is
PersistentVolume (PV)	A piece of storage in the cluster.
PersistentVolumeClaim (PVC)	A request for storage by a workload.
StorageClass	A template for dynamically provisioning PVs.

Access modes¶

Mode	Meaning
`ReadWriteOnce` (RWO)	Mounted read-write by one node
`ReadOnlyMany` (ROX)	Mounted read-only by many nodes
`ReadWriteMany` (RWX)	Mounted read-write by many nodes (needs a supporting backend)
`ReadWriteOncePod` (RWOP)	Read-write by a single Pod

Example claim¶

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: data
spec:
  accessModes: ["ReadWriteOnce"]
  storageClassName: standard      # use a class from: kubectl get storageclass
  resources:
    requests:
      storage: 10Gi

Things worth knowing¶

With volumeBindingMode: WaitForFirstConsumer, a PVC stays Pending until a Pod uses it. That is normal.
reclaimPolicy: Delete removes the underlying disk when the PVC is deleted. Use Retain for data you cannot lose.
Growing a volume needs allowVolumeExpansion: true on the StorageClass.

kubectl get pvc,pv -A
kubectl describe pvc <name>

Having trouble? See Storage troubleshooting.