moving /usr to another partition

Hi!

Diskspace is running low, so I'd like to move my /usr to another
disk. I was told that cp -Rv is not a good idea and i should use
dump instead. The problem is: That disk is big and half-full and
I don't want to empty it. Is it possible  to let restore work to
a directory instead of a disk? Im not sure after reading the man
page, google doesnt know either and I dont want to find out "the
hard way". So i guessed it couldn't hurt to ask...

If you have any hints or alternatives, please let me know!

cya,
Kosta