Active Roles will subscribe to an Active Directory Domain Controller so that it can receive notifications about new and replicated Active Directory events. This behaviour is controlled by the DirSync Server Selection screen which can be found within the Active Roles Console:
There are three settings on this screen. These settings can be changed at any time, as Active Roles will gracefully complete the current operation and then change over to use a new Domain Controller if the new settings require it:
Any available domain controller: This is the default option. This is the best option for redundancy, but this is not the best option for performance. In this configuration, Active Roles will fail over the any available Domain Controller if the current Domain Controller stops responding. This may also mean that Active Roles may end up communicating with a remote Domain Controller, and that latency with this new Domain Controller may negatively impact the performance of the Active Roles solution.
Any available domain controller in the site: This is the best option for both redundancy and performance, assuming that the site local to the Active Roles Administration Service node is selected and that this site has more than one Domain Controller. For the best redundancy, also select the checkbox labeled Temporarily switch to any available domain controller if there are no available domain controllers in the specified site
Only specified domain controller: This option should only be used during troubleshooting, to ensure the Active Roles Administration Service node is tied to a specific Domain Controller so that events and operations can be more easily traced. This option should not be used as a permanent configuration in a production environment because it offers NO redundancy. If the specified Domain Controller is unavailable, Active Roles will not be able to create a subscription to Active Directory.