Question

You have created a single PersistentVolume named 'data-pv' with capacity 50Gi, accessModes ReadWriteOnce, and no storageClassName. Two PersistentVolumeClaims are pending: 'claim-a' requests 20Gi ReadWriteOnce, and 'claim-b' requests 20Gi ReadWriteOnce. Both PVCs have no storageClassName set. After a few moments you observe that 'claim-a' is Bound to 'data-pv' but 'claim-b' remains Pending. Why does 'claim-b' stay Pending?

Accepted Answer

A PersistentVolume can only be bound to one PersistentVolumeClaim at a time, so the remaining 30Gi of 'data-pv' cannot be shared with 'claim-b'.

Answer

'claim-b' requests ReadWriteOnce, which prevents it from binding to any volume already bound by another claim, but ReadWriteMany would have allowed it to share 'data-pv'.

Answer

The PV's remaining capacity (30Gi) is insufficient because Kubernetes reserves 50% overhead on hostPath volumes.

Answer

'claim-b' must specify a storageClassName matching the PV in order to bind, while 'claim-a' bound because it was created first.