You also might check out rdiff-backup if you just want to back up the data and don't "need"
to clone the disk.
If you do use it make sure you put the backup on its own partition. That way if you make a
mistake and cause rdiff-backup to run wild and fill up the partition it won't shut down the
I've been using it for 10 years and it is cast iron stable. There are also lots of features
as to what gets backed up and how long to keep past incremental backups.
Also, you can use "kickstart"
installing from network is possible
If disks geometry are the same, you can copy disk physically by "dd" command
CentOS rescue is mini cd and you can rescue disk boot system and chroot /mnt/sysimage
then you can restore system.
Depending on a number of variables, there are multiple ways to accomplish your goal. Take a
look at using dd to copy the entire disk contents over to a hard drive mounted in a USB dock
connected directly to the server. This will give you a bootable, portable solution. I've
found this this to be a simple, quick reliable solution and gets away from the cd/dvd