At work, we host all our webservers on Amazon EC2 and usually have used MySQL databases installed on the same box as our Apache webserver, and communicated with them on
localhost. We now face a need to migrate our database to its own server for one of our systems. I have a choice between two solutions: use Amazon RDS, or just launch a new Amazon EC2 box and install MySQL on it.
RDS, being a dedicated database service provided by the same company as EC2, seems like it ought to be the obviously better option. However, when I look at the pricing for the two options (see http://aws.amazon.com/ec2/pricing and http://aws.amazon.com/rds/pricing) it seems that an RDS server costs almost twice as much as an EC2 server for a box with the same specs.
Given that I'm capable of handling backups myself and that EC2 offers the same ability to scale up the instance as required that RDS does, I can't see any reason at all to use RDS instead of EC2. It seems like I'm probably missing something big, though, because if I were right, nobody would use RDS. What exactly am I missing, and what are the advantages of RDS over installing your own database on an EC2 instance?