If you manage a few dozen servers or more, maintain a couple of applications or even websites, you owe it yourself to use some kind of Version Control Systems. Something like CVS, SVN or maybe even Git. Alternatively, you can use something like cfEngine to keep all servers configured similarly. However, CVS or SVN can store working versions of all important in one place and provide you will roll-backs if worse comes to worst. Application servers create little config files like crazy and getting a release frozen into SVN, using a subversion tag, can be a life saver at times.