How Smart are the iCloud Backups?

[Statelymwhite]

Does it only backup new or modified files, or does it dump and overwrite everything? My three devices total 1.6GB in data, and I'll hit my Comcast 250GB in no time if it's uploading 1.6GB every time I plug one of them in.

 

[Saberon]

Only backs up the changes.

 

[Statelymwhite]

Thanks