I want to scale my Drupal site and I was wondering how to approach it with Drupal and Amazon EC2. This is a bit related to [How to use Drupal in the cloud with on demand instances](https://drupal.stackexchange.com/questions/224/how-to-use-drupal-in-the-cloud-with-on-demand-instances).

With Amazon, I can monitor my server and if certain metrics are hit then it can launch a new instance that is load-balanced. My questions are then:

* Does Drupal create specific files as users do stuff? Is everything on the database? (I have a separate database server that all my nodes point to.)
* Are sessions local or is it on the database as well? I'm thinking of situations where user connects to server A and then gets moved to server B. Would the user lose anything?

If it helps, I'm using Drupal 6.