When you clone a first hard disk onto a second hard disk you force the second hard disk to become a mirror image of the first. Both disks have identical partition table and inside the area prescribed by this partition table every binary bit is the same in the two disk. Formatting the second disk is just a waste of time regardless you can get it right or not. The second disk by default will have the same geometry of the former.
Both CentrOS and Red Hat use a Linux boot loader which can be Lilo or Grub. Grub is the preferred choice in all the versions I have come across these two distros.
Any Grub, be it a Grub1 or Grub2, can boot any Linux directly
. Additionally a decent boot loader like Grub can indrectly
boot any other PC boot loader from Windows, BSD and Solaris.
Therefore there is no installed PC operating system Grub cannot boot!!!!!!!!!!!!!
If you must see a link to convince yourself this thread
has one Grub booting 145 operating system using indirfect method because it is easier. Red Hat and CentSO were the 2 among the 145 system. They were installed in hda11 and hdc11 respectively.