CSI documentation update for raw block volume support (#8927)

* CSI documetation update for raw block volume support

* minor edits for "CSI raw block volume support"

Some small grammar and style nits.

* minor CSIBlockVolume edits

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

@@ -1153,6 +1153,26 @@ persistent volume:
   secret is required. If the secret object contains more than one secret, all
   secrets are passed.
 
+#### CSI raw block volume support
+
+{{< feature-state for_k8s_version="v1.11" state="alpha" >}}
+
+Starting with version 1.11, CSI introduced support for raw block volumes, which
+relies on the raw block volume feature that was introduced in a previous version of 
+Kubernetes.  This feature will make it possible for vendors with external CSI drivers to 
+implement raw block volumes support in Kubernetes workloads.
+
+CSI block volume support is feature-gated and turned off by default.  To run CSI with
+block volume support enabled, a cluster administrator must enable the feature for each
+Kubernetes component using the following feature gate flags:
+
+```
+--feature-gates=BlockVolume=true,CSIBlockVolume=true
+```
+
+Learn how to 
+[setup your PV/PVC with raw block volume support](/docs/concepts/storage/persistent-volumes/#raw-block-volume-support).
+
 ### FlexVolume
 
 `FlexVolume` is an out-of-tree plugin interface that has existed in Kubernetes

content/en/docs/reference/command-line-tools-reference/feature-gates.md

@@ -40,6 +40,7 @@ different Kubernetes components.
 | `CPUManager` | `true` | Beta | 1.10 | |
 | `CRIContainerLogRotation` | `false` | Alpha | 1.10 | 1.10 |
 | `CRIContainerLogRotation` | `true` | Beta| 1.11 | |
+| `CSIBlockVolume` | `false` | Alpha | 1.11 | 1.11 |
 | `CSIPersistentVolume` | `false` | Alpha | 1.9 | 1.9 |
 | `CSIPersistentVolume` | `true` | Beta | 1.10 | |
 | `CustomPodDNS` | `false` | Alpha | 1.9 | 1.9 |
@@ -152,6 +153,7 @@ Each feature gate is designed for enabling/disabling a specific feature:
    for more details.
 - `CPUManager`: Enable container level CPU affinity support, see [CPU Management Policies](/docs/tasks/administer-cluster/cpu-management-policies/).
 - `CRIContainerLogRotation`: Enable container log rotation for cri container runtime.
+- `CSIBlockVolume`: Enable external CSI volume drivers to support block storage. See the [`csi` raw block volume support](/docs/concepts/storage/volumes/#csi-raw-block-volume-support) documentation for more details.
 - `CSIPersistentVolume`: Enable discovering and mounting volumes provisioned through a
   [CSI (Container Storage Interface)](https://github.com/kubernetes/community/blob/master/contributors/design-proposals/storage/container-storage-interface.md)
   compatible volume plugin.