Single cluster mode turns off load balancing between machines in an ArcGIS Server site containing one cluster. This reduces network traffic between machines in the site, reduces load on your network, and helps improve monitoring of GIS servers in your site. At 10.4 and later, this mode is the default for new installations of ArcGIS Server; when upgrading to version 10.5.1 and later, the mode will be enabled for sites with a single cluster that are not currently using single cluster mode. Single cluster sites already using single cluster mode and sites with multiple clusters at earlier releases will have their settings preserved when upgrading.
At 10.6, ArcGIS Server sites with multiple clusters have been deprecated. The use of multi-cluster sites for new deployments is strongly discouraged and existing deployments are advised to migrate away from use of multi-cluster sites as part of ongoing maintenance and upgrades. Single cluster mode is the recommended setting for all deployments.
When using single cluster mode, all GIS servers in the site must participate in a single cluster. Multiple clusters cannot exist.
An external load balancer or ArcGIS Web Adaptor must be configured to forward requests to the GIS servers in the site when single cluster mode is on. If no external gateway exists, requests will only be handled by the GIS server designated in the request.
You can disable single cluster mode to allow load balancing between machines in a single cluster. You must also disable it to create new clusters. Follow these steps to disable single cluster mode:
- Open the ArcGIS Server Administrator Directory and log in with an account that has administrative privileges to the site. The Administrator Directory is typically available through a URL such as https://gisserver.domain.com:6443/arcgis/admin.
- Click System > Deployment > Update.
- Click the Single Cluster Mode drop-down dialog box and select FALSE.
- Click Update. All GIS servers in the site are restarted.
- Restart the ArcGIS Server service on each machine using stopserver.sh and startserver.sh.
After the GIS servers restart, load balancing will now occur between machines in your site.