Setting up a Secondary Azure AD Connect Server in Staging Mode
If you are already using Azure Active Directory Connect to sync your on-premise Active Directory to Azure AD, then you should set up a secondary server for a backup. This second server can run in ‘staging’ mode, which means it can still be active but it will not sync any changes with Azure AD. If your primary sync server were to run into issues, you can easily flip your second sync server into active mode.
Agent Install
Download the latest agent on a second domain controller: Download Link
Launch the installer, accept the license terms and click continue
Clicking customize will show you some advanced settings. For this example, I am going to stick with the express settings
Enter the credentials for an Azure AD global admin account
Enter the credentials of an AD enterprise admin account
On the final screen, leave the “Start the synchronization process…” option unchecked
Configuring Staging Mode
Reopen Azure AD Connect, and choose Configure
Select the Configure staging mode task and click Next
Check “Enable staging mode” and click Next
On the final screen, this time you do want to check the option to start the sync process. Microsoft’s documentation explains why: “It is recommended to leave the sync process on for the server in Staging Mode, so if it becomes active, it will quickly take over and won’t have to do a large sync to catch up to the current state of the AD/Azure AD sync.”
Done!