Ultrasound uses two servers for reference: a replica member and a domain controller. Ultrasound chooses these servers based on logic described in these sections, but in some situations you might want to change the reference servers.
The reference replica member contains what Ultrasound considers the master set of files in a replica set. The reference member is used to collect per-file metadata, such as the full path, change history, file size, and last change time. With this metadata, the reference member is able to translate file GUIDs into file names and provide rich information about backlogged files, excessive replication, and sharing violations. This information is collected only from the reference replica member for performance and bandwidth reasons.
For a given replica set, Ultrasound chooses a default reference replica member that is in the same site as the controller. If multiple replica members exist in the same site as the controller, Ultrasound chooses the reference replica member by using the following criteria:
If you change the reference replica member, pick one that is in the same site as the controller. The reference member should be a highly available server, preferably where the majority of file changes originate. For single-master scenarios, choose the reference member acting as the single master. For information about changing the reference replica member, see To change the reference replica member.
If no replica member exists in the same site as the controller, Ultrasound does not choose a reference member and sends an alert to notify you of this situation. Until you choose a reference replica member, Ultrasound cannot track files or calculate some aggregate file size values.
The controller uses the reference domain controller to retrieve topology information from Active Directory. When you install Ultrasound, it chooses the closest domain controller as the reference domain controller. You might want to change the reference domain controller if you have experienced Active Directory replication issues; in this case, you might prefer to choose the PDC emulator master instead. If possible, use the same reference domain controller for multiple replica sets to ensure that Ultrasound shows a synchronized view of the FRS topology information retrieved from Active Directory for all the monitored replica sets.
By default, the controller polls the reference domain controller every eight hours to collect FRS topology information from Active Directory, though you can change the schedule if you want. When the database is updated, Ultrasound updates the delta (change) tables to reflect the differences. This information is useful if you need to understand what, if any, topology changes occurred around the same time as the FRS problem appeared.
If the reference domain controller fails or is unavailable due to network problems or other issues, an alert notifies you that the reference domain controller is unavailable. If a reference domain controller is demoted, Ultrasound chooses a new reference domain controller and sends an alert to notify you of this operation.
For information about changing the reference domain controller, see To change the reference domain controller.