We are performing massive upgrade project, where CM site server will be upgraded with Windows 2012 -> 2019, SQL 2014 -> 2019, and CM in-console upgrade from 2006 to 2013. I know, that officially snapshots and reverting to backup source are not supported. I am planning to keep SQL and SMS services shut down as much as possible during the upgrade to disallow all the client activity.
Our main concern is, that if something happends during Windows 2012 -> 2019 upgrade and we would be forced to recover back to 2012, what would then happen to all AD & SQL authentifications, AD account etc. Because in CM, you can't delete computer account of site system, you can' rename it, you can't rejoin the site server back to the AD domain services. Would recovered 2012 system get back to domain fine? WHat will happend with computer account etc.