RAID is simply not for backups, security, or data redundancy or any kind. It's specifically designed to keep a system running - think of it like having a spare drive, so if one dies, your computer doesn't crash. (alternatively if you play board games, its perhaps akin to having an extra 'wound' - you're still alive if you take 1 hit
That said, it has nothing to do with the redundancy of actual data (RAID 0 is a trivial case since it doesn't improve Uptime OR data redundancy).
Data backup involves creating a copy of the data (or an image or clone of the OS, or both, all depending on what you want backed up), and storing it on a DIFFERENT drive/system/site/network/planet to ensure that data loss in one place (an HDD dies) does not destroy the data itself, since you have a 'backup copy' somewhere else.
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RAID for servers, again, is about keeping the server online no matter if a drive fails - Uptime for servers is extremely important in the enterprise environment, hence the use of RAID, despite its MANY problematic disadvantages.
RAID 1 (not my favorite flavor of RAID) DOES NOT DO what it seems to do on the surface. It DOES NOT simply clone the drive onto a second paired drive. It does something else.
RAID 1 sets up a meta-data template on one drive, and when data is written to that drive, it copies it to the second (and 3rd, 4th etc) member of the array WITH the meta-data given it by the RAID controller (either hardware or software).
So the RAID controller, if you like, is in charge - it is important to remember that RAID adds the complexity of a RAID controller to the equation of data storage, it's not just the disks that are involved anymore.
RAID 1 allows the volume mapped across the drives to survive 1 drive failure (presuming you have 2). i.e. the drive will fail, the system to switch to the other drive, and will alert you to replace the failed HDD. It will then rebuild the array.
HOWEVER, let's say your RAID controller dies, rather than the disks themselves. YOU WILL NOT (ceteris paribus) be able to simply grab a RAID 1 member HDD, plug it into a machine, and access the data. That data, as mentioned before, has been written to the drive by the RAID CONTROLLER with meta-data, offsets, etc. which make it unreadable for the most part save for the controller which wrote it.
(There are sophisticated ways, and just software, which in theory allow the reconstruction of data like this, but I personally have never seen them work, then again I'm not a sysadmin or anything, so perhaps they use them regularly and I just don't know).
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As for the prices and the specific drives - I find it unlikely that a home server will see any benefit from different HDD products from the manufacturers - yes some HDDs are 'enterprise class' and are designed to work well/better with RAID setups, but in terms of failure rates, etc., I doubt there will be a pronounced difference. Drives fail, period. Hence the RAID in the first place.