Depending on your server OS (Unix, freebsd, windows), there are a multitude of file syncronization programs out. A friend of mine used a php script to ftp all files to another server in a cron job.
!/usr/bin/php or some syntax like that on a freebsd server. There's even software from iopus that emails chainged versions (b2ee=better to email everything...i thunk).
possibly something similar to this
Have fun searching trying to figure out if the two files are the same.