When the SnapManager MMC snap-in connects to a Database Availability Group (DAG), all mailbox databases in the DAG, including both the active and passive databases, are displayed. If the SnapManager MMC snap-in connects to a member server of the DAG, only the mailbox databases on that server are displayed.
When you connect to the DAG in the Scope pane, you can view all the databases in the DAG that are available for backup. When you connect to a member server of the DAG, you can view and back up the databases on that server only.