Architecture of MySQL on EBS for scaling (Amazon Web Services)

I'm trying to understand how to architect an Amazon Web Services application.

I have an instance running off of EBS. As far as I understand, I need to mount the EBS drive so that I can store my MySQL database on it.

When I later want to scale up, how do I do so? I understand that I can add more server instances, but how will they be accessing the database? Since from what I understand, the EBS volume can only be attached to one server instance.

I can't speak to this particular setup as I do not have experience using EBS with a MySQL instance but how this type of scaling is typically accomplished is by dedicating a particular instance as the master database server. Any time you spin up additional web servers those are still using the master DB IP to connect. At the time in which your database is the bottleneck you then spin up a slave DB instance on one of the boxes (or its own dedicated box). You can then configure replication in either a master to slave direction or a circular replication so that you can write to the slave instance as well.

If you choose the classic master to slave replication then you will have to make sure your writes are only performed on the master DB instance.

You can setup something like Zeus or any other connection load balancer so that you only ever have to connect to a single Database IP which will then round-robin route your read connections to your pool of servers. Otherwise you'd have to manage the connections yourself which is definitely not trivial. Good luck.

Growing Amazon EBS Volume sizes

You can give a try to MySQL clustering on your EBS backed instances. I have similar query, with more requirements, posted here.

EBS Volumes capacity can be scaled up using Snapshot->launch new volume technique, alternatively storage capacity can be scaled out using EBS Striping (RAID 0).

In AWS you cannot mount same EBS Volume to 2 EC2 instances simultaneously, so when you are scaling your application you need to scale out / up your MySQL DB either thru Replication or clustering. AWS RDS is a very good option for MySQL , if your application is read intensive then you can scale out using RDS Read replica's as well. If you need write scaling then functional partition or MySQL Shards can be explored.

AWS has an entire product dedicated to this: RDS.

In all but the rarest and most specialized of circumstances you're going to be better off using RDS than trying to create and tune your own EBS/EC2/MySQL infrastructure.

RDS also directly answers your question - they directly enable the creation of readonly databases to use as query slaves. RDS also performs backups, upgrades, and all sorts of fail-over infrastructure for you.

With EBS there's no way to attach a disk to multiple EC2 instances, so you're not going to be able to build out a failure cluster using that approach. Instead you're going to need replication or backup tools of some type.