We're testing deployment of a web app on Amazon's EC2 which uses MongoDB for the database. Mongo recommends using at least 3 nodes for replication for data integrity. Although this is testing, we'd like to test with replication to see how the system handles failures, so we need 3 EC2 instances at a minimum. I'd also like to see that web load balancing works as well.
My thinking is to create 3 medium EC2 instances all running both MongoDB and the web server. We'll have a load balancer distribute web requests between the three servers, and configure Mongo to use them as replicas for data integrity.
Are there any problems with this plan?