Unfortunately EXT type of file systems do not support this as others have posted about there are many other ways to do back ups.
You might want to look at BTFS it is still experiential at this time but it have many cool features built in that I think you are looking for
http://en.wikipedia.org/wiki/Btrfs
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Unfortunately EXT type of file systems do not support this as others have posted about there are many other ways to do back ups. You might want to look at BTFS it is still experiential at this time but it have many cool features built in that I think you are looking for http://en.wikipedia.org/wiki/Btrfs