Sonar is a tool designed for monitoring key statistics about FRS members in a replica set. Sonar can collect basic status information from FRS running on either Windows 2000 (all service packs), or Windows Server 2003. You can use Sonar to easily watch coarse statistics on a replica set, and to monitor traffic levels, backlogs, free space, and other issues. Sonar allows definition of filters that define rules for which rows to display, and also allows definition of column sets that can be viewed. Sonar does not modify any settings on the computers that you monitor; it just passively reads information.
Note that the Sonar display is member-oriented — it tries to roll-up statistics into a per-member view, instead of a connection-specific view. This is by design; Sonar provides a way of monitoring a set at a high level for members that are in trouble. However, the actual trouble might be connection-specific, so troubleshooting often involves first finding a member that requires attention by using Sonar, and then drilling into the connection-specific issues by using other tools, such as FRSDiag or the Perl scripts. For more information about these tools, see FRS Data Collection Scripts.