We use Dropbox to store and sync quite a few large files between multiple machines and users.

What we where wandering is if you have a 100MB file and it gets uploaded once, (and downloaded to all other machines once) then you make a change to that file, Dropbox will now try to re sync that file, is it re syncing the whole file or can it work out the changes and just sync them?

I.e. does it sync 100MB each time or just the changes, say circa a couple of mb?

I know that they used to sync the whole file each time, but the post I found (on an external blog) saying that was 2 years old, and I wandered if anything has changed since.