When most Group Policy settings are changed, these changes can often be applied during periodic background refresh of Group Policy. Folder Redirection (FR) is an exception however; changes to your FR policy are processed synchronously and so only take effect upon the user's next logoff.
Why is FR different from most other policy settings? It's simple. Let's say you modified FR policy to change the redirected location for a user profile folder like My Documents. Then let's say FR policy was processed in the background while some documents were being copied from the user's My Documents folder to the redirected location on the server. The result could be file corruption, with one part of the file being copied to the old location and the rest of the file copied to the new location. In order to prevent the possibility of such file corruption, FR policy was designed to be processed only on logoff.
Understanding how Group Policy works under the hood like this is essential if you want to become adept at troubleshooting issues arising from how Group Policy is processed in Active Directory environments.
Mitch Tulloch is a seven-time recipient of the Microsoft Most Valuable Professional (MVP) award and widely recognized expert on Windows administration, deployment and virtualization. For more tips by Mitch you can follow him on Twitter or friend him on Facebook.