I have my first domain controller on an Amazon EC2 instance, which is only used for service and administrative accounts for a handful of servers.
I would like to avoid the expense of another server just for an additional domain controller, and was wondering if I could install it on the database server.
Given the light domain usage scenario, would the additional domain controller significantly affect the performance of the database server? Are there other reasons why I shouldn't take this approach?
Edit: Removed the terms "primary" and "backup" DCs. :)
Update: The DB Server is SQL 2008 R2 on Win 2008 R2. The domain controller is SQL 2008 SP2.