Ask HN: How to backup database?

I've been looking to deploy my first rails app. I've decided to go with dedicated server, and move to cloud, if it grows large.

Since, the application will host user data, I want to be safe on hard disk crashes, Especially I want to backup databases.

Is it okey to have db on the same machine, or should I go for services like amazon rds for safety?

In case of backups, What solutions work well, to backup databases offsite?