Merge branch 'docs-pages-standalone-deployment' into 'master'

Adds steps for running GitLab Pages on a separate server

See merge request gitlab-org/gitlab-ce!24256

doc/administration/pages/index.md

@@ -332,6 +332,42 @@ The maximum size of the unpacked archive per project can be configured in the
 Admin area under the Application settings in the **Maximum size of pages (MB)**.
 The default is 100MB.
 
+## Running GitLab Pages in a separate server
+
+You may want to run GitLab Pages daemon on a separate server in order to decrease the load on your main application server.
+Follow the steps below to configure GitLab Pages in a separate server.
+
+1. Suppose you have the main GitLab application server named `app1`. Prepare 
+new Linux server (let's call it `app2`), create NFS share there and configure access to 
+this share from `app1`. Let's use the default GitLab Pages folder `/var/opt/gitlab/gitlab-rails/shared/pages` 
+as the shared folder on `app2` and mount it to `/mnt/pages` on `app1`.
+
+1. On `app2` install GitLab omnibus and modify `/etc/gitlab/gitlab.rb` this way:
+
+    ```shell
+    external_url 'http://<ip-address-of-the-server>'
+    pages_external_url "http://<your-pages-domain>"
+    postgresql['enable'] = false
+    redis['enable'] = false
+    prometheus['enable'] = false
+    unicorn['enable'] = false
+    sidekiq['enable'] = false
+    gitlab_workhorse['enable'] = false
+    gitaly['enable'] = false
+    alertmanager['enable'] = false
+    node_exporter['enable'] = false
+    ```
+1. Run `sudo gitlab-ctl reconfigure`.
+1. On `app1` apply the following changes to `/etc/gitlab/gitlab.rb`:
+
+    ```shell
+    gitlab_pages['enable'] = false
+    pages_external_url "http://<your-pages-domain>"
+    gitlab_rails['pages_path'] = "/mnt/pages"
+    ```
+    
+1. Run `sudo gitlab-ctl reconfigure`.
+
 ## Backup
 
 Pages are part of the [regular backup][backup] so there is nothing to configure.