// It must meet the same requirements as the name of a StorageClass
  // object (non-empty, DNS subdomain). If that object no longer exists,
  // the CSIStorageCapacity object is obsolete and should be removed by its
  // creator.
  // This field is immutable.
  optional string storageClassName = 3;

  // capacity is the value reported by the CSI driver in its GetCapacityResponse