Microsoft released Availability Groups (AG) as a feature in SQL Server 2012. Prior to SQL Server 2016, there were two methods of adding a database to a new AG replica.
- You could provide the Add Database to Availability Group wizard a file share accessible by the primary and secondary replicas. SQL Server would run FULL and LOG backups of each database to the share and use them to restore the database(s) to each replica.
- You could manually run a FULL and LOG backup of each database, copy the backup files to each replica, and restore the databases WITH NORECOVERY.
With SQL Server 2016. Microsoft has provided a third option, Automatic Seeding. With Automatic Seeding, you specify the databases and the replicas and SQL Server will begin transferring data to each replica. The duration of the seeding process depends on the size of the database and the network bandwidth available between primary and secondary replica.
Automatic seeding isn’t perfect, but it’s quite useful.