To the sysadmins out there, I'm trying to get an idea about how you go about maintaining redundant servers for small projects. The modest number of servers in my mind is two, and three main essential services come to mind: HTTP, mail and DNS. How do you automate this duplicity? Is rsync the tool of choice (again, for small projects)?
In addition to common tools for these tasks, references to books and articles would be greatly appreciated. The more hands-on the approach, the better.