Cloning disks in that manner is less than
optimal.  Garbage may go along for the ride.
I am assuming you mean something like dd'ing
from one drive to the other.  In my experience
that should be used only for emergency recovery
regardless of what condition the drive is in, or
to take a few blocks of disklabel from one drive
to another, or to zero out a disk.

The best way to clone, I was taught, is to

1. format the drive if required.
2. label with disklabel.
3. newfs the file systems needed.
4. cyclically dump/restore between the required
   file systems.
5. write boot blocks if needed.

If I need to do more than one or two drives in
this way, it is convenient to write a short
script to do that.

Good Luck

Bob Keys