Document Geo pause/resume single-node limitation

doc/administration/geo/index.md

@@ -208,7 +208,9 @@ Omnibus GitLab-managed database. External databases are currently not supported.
 
 In some circumstances, like during [upgrades](replication/updating_the_geo_nodes.md) or a [planned failover](disaster_recovery/planned_failover.md), it is desirable to pause replication between the primary and secondary.
 
-Pausing and resuming replication is done via a command line tool from the secondary node.
+Pausing and resuming replication is done via a command line tool from the secondary node where the `postgresql` service is enabled.
+
+If `postgresql` is on a standalone database node, ensure that `gitlab.rb` on that node contains the configuration line `gitlab_rails['geo_node_name'] = 'node_name'`, where `node_name` is the same as the `geo_name_name` on the application node.
 
 **To Pause: (from secondary)**
 

doc/administration/geo/replication/multiple_servers.md

@@ -173,6 +173,12 @@ the **primary** database. Use the following as a guide.
    ##
    roles ['geo_secondary_role', 'postgres_role']
 
+   ##
+   ## The unique identifier for the Geo node.
+   ## This should match the secondary's application node.
+   ##
+   gitlab_rails['geo_node_name'] = '<node_name_here>'
+
    ##
    ## Secondary address
    ## - replace '<secondary_node_ip>' with the public or VPC address of your Geo secondary node