Not an invalid copy of dvd
[COLOR="rgb(65, 105, 225)"]Suggestion: Talk to your instructor about using CentOS instead of RHEL. (I suspect that the instructor is in violation of the schools license when he distributed that RHEL DVD. It contains some copyrighted material.) The advantage of the CentOS is that is a copy (now supported by Red Hat as an in-house project) of the non-copyrighted parts of the current RHEL distribution, as a FOSS distribution.
About the RAID: I have a Fedora 20 installation on a single partition, and a Fedora 21 one on a RAID-1 pair of partitions (using mdadm) on two different drives, and the mirrored system is often twice as fast as the single-drive system. (Both systems are using etx4 file systems.)
On the other hand, if you're interested in data safety in a large shop (after you get your business going ), look at the Logical Volume Management system, and the snapshot backups you can do with it. (The btrfs automates the backup process, but, when I tried it on a volatile system, all the hard links "ate" 1.5Tb of my 2Tb test array in about two months. I think it could be better tuned, but I didn't want to struggle with that, so I dropped - for now - that file system.)[/COLOR]
I attended a valid Redhat Linux Training class and the DVD was provided by the instructor as part of the Redhat Course material as part of the class. I also want to use RAID 5 and have 3 hard drives setup in the system, but I need to partition them and load LINUX.