best way to copy a big binary file

[Skaperen]

nice article. but my need gives rsync no advantage. the target does not yet exist. this is an in-host copy of a very large file such as a movie video. it may be copying between two different filesystems. it may be doing a first-time full backup (even rsync has to do this the first time). i am wondering how good copy code determines what is a good chunk size to better manage memory load, or if it uses (some module).sendfile() and how.