Is rsync --append able to resume an interrupted copy process without reading all the copied data?

I need to copy one very large file (3TB) on the same machine from one external drive to another. This might take (because of low bandwidth) many days. So I want to be prepared when I have to interrupt the copying and resume it after, say, a restart. From what I've read I can use rsync --append for this (with rsync version>3). Two questions about the --append flag here: 1. Do I use rsync --append for *all* invocations? (For the first invocation when *no* interrupted copy on the destination drive yet exists and for the subsequent invocations when there *is* an interrupted copy at the destination.) 2. Does rsync --append resume for the subsequent invocations the copying process _without_ reading all the already copied data? (In other words: Does rsync mimic a dd-style seek-and-read operation ?)