We want to use AD as a regular LDAP for storing and accessing our application data in fast and reliable way. We have two physical server and want to organize some sort of clustering for AD and its data. What is the best-practice for such task?
AD is already clustered. You bind to the domain using the correct entries that AD has stored in DNS. Edit - to clarify :
Having said that, it's not a great idea to store much of your own data in AD's schema. You may want to make your own partition, or use LDS (formerly ADAM.)