Regional PD documentation; edited validation for Volumes page (#8714)

content/en/docs/concepts/storage/volumes.md

@@ -368,6 +368,38 @@ spec:
       fsType: ext4
 ```
 
+#### Regional Persistent Disks
+{{< feature-state for_k8s_version="v1.10" state="beta" >}}
+
+The [Regional Persistent Disks](https://cloud.google.com/compute/docs/disks/#repds) feature allows the creation of Persistent Disks that are available in two zones within the same region. In order to use this feature, the volume must be provisioned as a PersistentVolume; referencing the volume directly from a pod is not supported.
+
+#### Manually provisioning a Regional PD PersistentVolume
+Dynamic provisioning is possible using a [StorageClass for GCE PD](/docs/concepts/storage/storage-classes/#gce).
+Before creating a PersistentVolume, you must create the PD:
+```shell
+gcloud beta compute disks create --size=500GB my-data-disk
+    --region us-central1
+    --replica-zones us-central1-a,us-central1-b
+```
+Example PersistentVolume spec:
+
+```yaml
+apiVersion: v1
+kind: PersistentVolume
+metadata:
+  name: test-volume
+  labels:
+    failure-domain.beta.kubernetes.io/zone: us-central1-a__us-central1-b
+spec:
+  capacity:
+    storage: 400Gi
+  accessModes:
+  - ReadWriteOnce
+  gcePersistentDisk:
+    pdName: my-data-disk
+    fsType: ext4
+```
+
 ### gitRepo
 
 A `gitRepo` volume is an example of what can be done as a volume plugin.  It
@@ -527,7 +559,7 @@ durability characteristics of the underlying disk.
 The following is an example PersistentVolume spec using a `local` volume and
 `nodeAffinity`:
 
-``` yaml
+```yaml
 apiVersion: v1
 kind: PersistentVolume
 metadata: