Add details for storage and knative services (#5605)

* add details for storage and knative services

* fixes

* Update storage.md

add missing whitespace

---------

Co-authored-by: Reto Lehmann <retocode@icloud.com>

config/nav.yml

@@ -131,6 +131,7 @@ nav:
           # TODO: Add security section to docs?
           - Configure resource requests and limits: serving/services/configure-requests-limits-services.md
           - HTTPS redirection: serving/services/http-protocol.md
+          - Volume Support: serving/services/storage.md
         - Traffic management: serving/traffic-management.md
         - Configuring gradual rollout of traffic to Revisions: serving/rolling-out-latest-revision.md
         - Tag resolution: serving/tag-resolution.md

docs/serving/services/storage.md

@@ -0,0 +1,40 @@
+# Volume Support for Knative services
+
+By default Serving supports the mounting the [volume types](https://kubernetes.io/docs/concepts/storage/volumes): `emptyDir`, `secret`, `configMap` and `projected`. [PersistentVolumes](https://kubernetes.io/docs/concepts/storage/persistent-volumes/) are supported but require a [feature flag](../configuration/feature-flags.md) to be enabled.
+
+!!! warning
+    Mounting large volumes may add considerable overhead to the application's start up time.
+
+
+Here is an example of using a persistent volume claim with a Knative Service:
+
+```yaml
+apiVersion: serving.knative.dev/v1
+kind: Service
+...
+spec:
+  template:
+    spec:
+      containers:
+          ...
+          volumeMounts:
+            - mountPath: /data
+              name: mydata
+              readOnly: false
+      volumes:
+        - name: mydata
+          persistentVolumeClaim:
+            claimName: knative-pv-claim
+            readOnly: false
+---
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: knative-pv-claim
+spec:
+  accessModes:
+    - ReadWriteOnce
+  resources:
+    requests:
+      storage: 1Gi
+```