I realize a couple of basic differences between the two, i.e.
EC2 is going to be cheaper
RDS I wouldn't have to do maintenance
Other than those two, are there any advantages to running my database from RDS as opposed to a separate EC2 server acting as a MySQL server. Assuming similar instance sizes, are both going to run into the same limitations in terms of being able to handle a load?
To give you a little bit more info about my use, I've got a database, nothing too big or anything (biggest table 1 million rows), just high SELECT volume.
I have been trying out RDS for a few months and here are some issues I have:
Using SQL profiler is tricky. Since you cannot connect profiler directly to the server, you have to run some stored procedures to create a log file that you can analyze. While they offer some suggestions about how that is done, it is far from user friendly. I would only recommend that you have a certified SQL professional do this kind of work.
while Amazon backs up your instance, you cannot restore an individual database. I have a web app with several separate customer-specific databases and my solution was to launch an EC2 instance with SQL running on it to attach to the production RDB database and import the data and then back it up on the EC2 instance. The other solution was to use a 3rd party tool that creates a massive SQL script (on the app server) that will recreate the schema and populate the data back to a restore point.
We chose to use EC2 MySQL instances because we have a high read volume and need master-slave replication. Of course, you can spin up multiple RDS instances and setup MySQL replication between them yourself, but we use Scalr.net, which manages that for you using EC2 instances.
Basically, we just tell Scalr how many MySQL instances we want at it keeps them up, automates the setup of replication, handles automatic failover of slave promotion to master if the master gets terminated etc. It does both SQL dump backups and EBS volume snapshots of the master. So, when it needs to create a new slave, it automatically temporarily mounts an EBS volume of the last master snapshot to initialize the slave DB, then starts replication from the appropriate point. All point and click :) (and no, I don't work for Scalr or anything. Scalr is available as Open Source if you don't want to use their service)