Concepts
Recovery Time Objective (RTO) – the maximum acceptable time to recover time to recover data and resume processing after a failure.
Recovery Point Objective (RPO) – maximum period of acceptable data loss.
With RDS you can take EBS volume snapshots of your database instances, snapshots include all database on the instance and are store in S3.
Taking a snapshot suspends all I/O operations for a few seconds, unless using multi-AZ. SQL Sever has always an I/O suspension during snapshots.
Automated Snapshots
RDS can automatically create snapshots of your instances daily during a 30 minute backup window.
Enabling automatic backups enables point-in-time recovery, which archives database change logs to S3 every 5 minutes, restoring point-in-time backups can take hours depending on the amount of data.
RDS keeps automated snapshots for a limited period of time (default 7, max 35 days) one can choose a retention period between 7-35 days.
Snapshots are disabled if the period is set to 0, this also deletes all existing backups and disables point-in-time recovery. Changing from 0 to any other value will trigger an immediate snapshot.
You can also take a manual snapshot of the database instances and this will remain until you delete them.