rsync
 

Can rsync backup data to another disk on the same machine instead of a remote host

yes this works also, an possible use is limit the bandwith of a kind of incremental backup.

you can even use it to make copies from special filesystems like for instance clearcase (version management) which add a local layer over files on a server. by using rsync with bandwith limit you can have your own copy

Look in ‘man rsync’ under ‘usage’ and ‘advanced usage’ for an extensive list of things you can do with rsync.

I almost never use cp for complicated stuff anymore.