Pero if the hard drive is "physically" damaged, then both partitions are kaput. Hehe, anyway, gets ko naman. Okay nga gumawa ng partition as a backup, as that "backup" partition may be saved if the other succumbs to a virus attack, or data corruption. Still, without the use of other programs, your backup is as far as resaving important files and documents, not creating an identical bootable drive which will have the same OS and settings.
Pero in terms of redundant identical backups on two identical separate hard drives... RAID 1 all the way!