You don't need to enable feature gate for using local-storage in kubernetes cluster after kubernetes 1.10.

You can directly use local-storage same as any other storage class.

Please have a look at my following answer, how to setup local-storage PV, PVC in kubernetes.

EDIT: As you're on kubernetes 1.9, you can do it this way:

You need to provide the feature-gates while starting the cluster using kubeadm init --config=config.yaml to apiserver, controller-manager and scheduler. Please refer following config:

 apiVersion: kubeadm.k8s.io/v1alpha1
 kind: MasterConfiguration
 apiServerExtraArgs:
   service-node-port-range: 80-32767
   feature-gates: "PersistentLocalVolumes=true,VolumeScheduling=true,MountPropagation=true"
 controllerManagerExtraArgs:
   feature-gates: "PersistentLocalVolumes=true,VolumeScheduling=true,MountPropagation=true"
 schedulerExtraArgs:
   feature-gates: "PersistentLocalVolumes=true,VolumeScheduling=true,MountPropagation=true"

Then you need to create your own storage class, as there is no local-storage class present. So create your own class as follow:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: local-storage-data
provisioner: kubernetes.io/no-provisioner
volumeBindingMode: WaitForFirstConsumer

Now you can create your PV and PVC in following way:

PV Definition:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: mysql-mariadb-0
  labels:
    pod-name: mariadb-0
  annotations:
    "volume.alpha.kubernetes.io/node-affinity": '{
      "requiredDuringSchedulingIgnoredDuringExecution": {
        "nodeSelectorTerms": [
          { "matchExpressions": [
              { "key": "kubernetes.io/hostname",
                "operator": "In",
                "values": ["prod-mysql-0"]
              }
          ]}
        ]}}'
spec:
  capacity:
    storage: 2Gi
  accessModes:
  - ReadWriteOnce
  persistentVolumeReclaimPolicy: Retain
  storageClassName: local-storage-data
  local:
    path: /mnt/local-storage/mysql-data-0

PVC definition:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  labels:
    app: mariadb
  name: mysql-mariadb-0
  namespace: mysql
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 2Gi
  storageClassName: local-storage-data
  selector:
    matchLabels:
      pod-name: mariadb-0

Is it possible to mount different pods to the same portion of a local persistent volume?

Hope this helps