message VolumeAttachmentSpec {
  // attacher indicates the name of the volume driver that MUST handle this
  // request. This is the name returned by GetPluginName().
  optional string attacher = 1;

  // source represents the volume that should be attached.
  optional VolumeAttachmentSource source = 2;

  // nodeName represents the node that the volume should be attached to.
  optional string nodeName = 3;
}

  // persistentVolumeClaimRetentionPolicy describes the lifecycle of persistent
  // volume claims created from volumeClaimTemplates. By default, all persistent
  // volume claims are created as needed and retained until manually deleted. This
  // policy allows the lifecycle to be altered, for example by deleting persistent
  // volume claims when their stateful set is deleted, or when their pod is scaled

  // fsGroupPolicy defines if the underlying volume supports changing ownership and
  // permission of the volume before being mounted.
  // Refer to the specific FSGroupPolicy values for additional details.
  //
  // This field is immutable.
  //
  // Defaults to ReadWriteOnceWithFSType, which will examine each volume
  // to determine if Kubernetes should modify ownership and permissions of the volume.

  // driver is the name of the Flexvolume driver.
  optional string driver = 1;
}

// AllowedHostPath defines the host volume conditions that will be enabled by a policy
// for pods to use. It requires the path prefix to be defined.
message AllowedHostPath {
  // pathPrefix is the path prefix that the host volume must match.
  // It does not support `*`.
  // Trailing slashes are trimmed when validating the path prefix with a host path.
  //

  // fsGroupPolicy defines if the underlying volume supports changing ownership and
  // permission of the volume before being mounted.
  // Refer to the specific FSGroupPolicy values for additional details.
  //
  // This field is immutable.
  //
  // Defaults to ReadWriteOnceWithFSType, which will examine each volume
  // to determine if Kubernetes should modify ownership and permissions of the volume.

}

// Represents storage that is managed by an external CSI volume driver (Beta feature)
message CSIPersistentVolumeSource {
  // driver is the name of the driver to use for this volume.
  // Required.
  optional string driver = 1;

  // volumeHandle is the unique volume name returned by the CSI volume
  // plugin’s CreateVolume to refer to the volume on all subsequent calls.
  // Required.