What should I consider when deploying a new web farm?

My web app has been chugging along just great in Production for years with one App server and one Web server. Now we're moving to a multi-server environment with 2 App and 3 Web servers. I have enough time to make changes before the go-live.

As a Developer, what 开发者_运维百科considerations should I take into account from coding, deployment, and architectural/ecosystem management perspectives?

Already on my list:

• Remove tight-coupling between servers
• Applicable files (i.e. downloadables) stored in IMAGE fields in SQL instead of files on app server
• Deployment: Take out node out of the farm at a time

Have you given any thought to sticky sessions and cache management?