Chapter 9 High Availability for FortiOS 5.0 : Virtual clusters : Virtual clustering overview : Virtual clustering and HA override
  
Virtual clustering and HA override
For a virtual cluster configuration, override is enabled by default for both virtual clusters when you:
Enable VDOM partionning from the web‑based manager by moving virtual domains to virtual cluster 2
Enter set vcluster2 enable from the CLI config system ha command to enable virtual cluster 2.
Usually you would enable virtual cluster 2 and expect one cluster unit to be the primary unit for virtual cluster 1 and the other cluster unit to be the primary unit for virtual cluster 2. For this distribution to occur override must be enabled for both virtual clusters. Otherwise you will need to restart the cluster to force it to renegotiate.
 
If override is enabled the cluster may renegotiate too often.You can choose to disable override at any time. If you decide to disable override, for best results, you should disable it for both cluster units.
For more information about HA override see “HA override”.