XCOPY was always my friend, it has some great memory management features. However it required scripting to get anything like a mirror of a directory structure, and it didn’t have shortcut features of copying only the changed part of a file.
The Wikipedia article has great information, as does the 35 page doc file that comes with the GUI. But it is super simple to set up a mirror script:
robocopy.exe c:/directory e:/backup MIR Z
There is a full list of robocopy switches at atlex.nl
Bye bye XCOPY, hello ROBOCOPY!