Hey - I think I get it. - LVM (Linux) or any other type of external snapshot (SAN snapshot, for example) is what you're looking for then, right?
On network load, agree that it's unavoidable - the question is the trade-off between host-level load versus network load. The trade-off always is whether you do a form of data reduction that takes cycles on the host machine (like rsync here - CBT elsewhere which theoretically has more data but puts much less load on the host machine) or whether you transfer raw bytes and do data reduction at the target.
