using carbon copy cloner to create two back ups on the same drive

"Can I create two or 3 partitions on my 1.5 t hardrive and allow carbon copy cloner to create two back ups of two different macs?"

Yes. Just use one partition for one backup, second partition for second backup, etc.
I do this all the time.

"If this must be done by using two partions on a single hardrive and the need ever arose to boot one of them up. How would I select the right partiton for rebooting ??"

1. Have backup drive connected, powered up
2. Reboot
3. As soon as you hear the startup sound, hold down the option key and KEEP HOLDING IT DOWN
4. In a few moments the startup manager will appear
5. You will see what to do next.
(Note -- selecting a boot source via the startup manager DOES NOT CHANGE the selection you made in the "Startup Disk" preference pane. The next time you reboot, the Mac will boot from that choice).

 

It's probably formatted in the Master Boot Record partition map scheme. In order for it to be bootable on an Intel Mac, you'll need to wipe it and repartition using the GUID Partition Map scheme instead. Unfortunately, this does require that you completely wipe the drive first. Hopefully, since it's for backups, there's nothing on there that will prevent you from doing that, if you need a bootable backup.

jW

 

Can you not set the two partitions up as a raid 1? Im sure you can.

If your doing this to have 2 back ups, then your defeating the purpose as if the drive dies you will still lose both partitions anyway.