Automatic initialization of SQL Server 2017 AlwaysOn AG (1)
Technical background
In SQL Server 2012 and 2014, the only way to initialize a secondary replica in an SQL Server Always On availability group is to use backup, replication, and restore.
SQL Server 2016 introduces a new feature for initializing secondary copies-automatic seed setting (automatic seeding). The automatic seed setting uses log streaming to stream backups using VDI to a secondary copy of each database that uses the availability group of the configured endpoint. You can use this new feature when you initially create an availability group or add a database to an availability group. All SQL Server 2016 and above that support AlwaysOn availability groups support automatic seeding and can be used with traditional availability groups and distributed availability groups.
