Duplicating a disk

Hi All,
  Does anybody know if it's possible and if so how difficult it is to
duplicate the hard drive? I want to switch over to a larger disk on my
system and I guess copy all my partitions from the 3 disks I have now onto
one bigger disk.
  I guess the hardest thing is to get the boot, root, var and tmp so the new
disk will bootup by itself and just copy the other partitions with the cp
command.
  It wouldn't hurt to have a backup disk either.

  Another thing I was thinking was just installing RH 8 on the new disk and
mounting the 7.2 disk for archive purposes. Can I do that? HAving a RH8 boot
disk and mount my 7.2 disks and just copy their data to the 8.0 disk?

 Thanks in advance.