ocprhv-694 disk preallocation - additions to RHV default install-config.yaml

Author: emarcusRH

modules/installing-rhv-example-install-config-yaml.adoc

@@ -34,13 +34,19 @@ compute:
 - architecture: amd64
   hyperthreading: Enabled
   name: worker
-  platform: {}
+  platform:
+    ovirt:
+      sparse: false <1>
+      format: raw   <2>
   replicas: 3
 controlPlane:
   architecture: amd64
   hyperthreading: Enabled
   name: master
-  platform: {}
+  platform:
+      ovirt:
+        sparse: false <1>
+        format: raw   <2>
   replicas: 3
 metadata:
   creationTimestamp: null
@@ -72,6 +78,13 @@ pullSecret: '{"auths": ...}'
 sshKey: ssh-ed12345 AAAA...
 ----
 
+<1> Setting this option to `false` enables preallocation of disks. The default is `true`. Setting `sparse` to `true` with `format` set to `raw` is not available for block storage domains. The `raw` format writes the entire virtual disk to the underlying physical disk.
+<2> Can be set to `cow` or `raw`. The default is `cow`. The `cow` format is optimized for virtual machines.
++
+[NOTE]
+====
+Preallocating disks on file storage domains writes zeroes to the file. This might not actually preallocate disks depending on the underlying storage.
+====
 
 [discrete]
 == Example minimal `install-config.yaml` file