high availability

I am researching how we can build a rolling deploy architecture for Drupal. Here is the high level goal:

1) I begin a software deploy, users are not affected by this
2) Software deploy is complete, users are not affected by this
3) I switch my load balancer such that only certain networks are directed at the new code, my internal testers test. External normal users are not affected by this.
4) After verification, I open the site wider, allowing a small % of normal users into the site. Most normal external users are not affected by this.

Hi All,

I'm thinking of an idea but not sure the pros/cons of it.

At the moment, we are hosting our website on a dedicated server. As a failover/load balanced solution, I'm thinking to use Amazon EC2+EBS.
The files can be rsync and mysql can be setup as master-master replication

When the load is high, I can up the machine, given sometime to "sync" and load balanced the traffic there.

is it do-able? any link I can read more on this?