1)what is recovery plan in place if something were to happen to AAD connect single server.
Solution:
Disaster recovery
Part of the implementation design is to plan for what to do in case there is a disaster where you lose the sync server. There are different models to use and which one to use depends on several factors including:
• What is your tolerance for not being able make changes to objects in Azure AD during the downtime?
• If you use password synchronization, do the users accept that they have to use the old password in Azure AD in case they change it on-premises?
• Do you have a dependency on real-time operations, such as password writeback?
Depending on the answers to these questions and your organization’s policy, one of the following strategies can be implemented:
• Rebuild when needed.
• Have a spare standby server, known as staging mode.
• Use virtual machines.
If you do not use the built-in SQL Express database, then you should also review the SQL High Availability section.
2) What are the disaster recovery procedure for single AAD connect server?Exporting configuration(.json) is not option for me because since 1.5.42.0 version exporting is supported and I need to upgrade from version before.
If single AAD connect server crashes is it possible to install on another server and configure it from beginning without backup?
Solution: We can backup current Azure AD Connect Configuration is "export Server Configuration", and we can export the settings if you go to File - Export Configuration.
In Azure AD Connect - File - Export ,You can backup. But you cannot use the backup from one server and feed it to another.
There is a AAD Connect Configuration Documenter tool which allows you to generate documentation of an Azure AD Connect installation.
Reference : ADConnect Backup Strategy (microsoft.com)==>https://social.msdn.microsoft.com/Forums/azure/en-US/88403abb-a013-4cf0-9a86-eea5ab0d402f/adconnect-backup-strategy
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