Scaling Amazon EC2 instanced when traffic to my app rises

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http://serverfault.com – I need your help about scalability on Amazon EC2 instanced. I have developed a web application using asp.net. I have decided that for start, I want to deploy it on a Medium High-CPU Windows Server 2008 instance. I have problem understanding what is Amazon Elastic Compute Cloud and what is CloudWatch Autoscaling and what each one does? My target: I want that when CPU utilization exceeds some kind of a limit, I want that Amazon will automatically create a duplicated instance (EC2 + EBS) from the current server and divide the visits between those two servers. When the stress is low, I want Amaz (HowTos)