I used to do this stuff for a living (file servers and such).
RAID stands for, take your pick, "Redundant Array of Inexpensive Drives", or "Random Array of Inexpensive Drives".
It's a bit misleading, since the discs were not exactly inexpensive, since RAID arrays place special demands on the disc drives.
There are various flavors of RAID, most of which I've thankfully forgotten, but they range from just mirroring two drives (like you have done) to having, say, a volume spanning three drives, with a fourth drive acting as a redundant drive that can step in and take over for any of the other three drives that might fail. It's cheaper than mirroring drives but it does require special software and controllers. And all the drives - at least when I worked in the industry - have to be pretty much identical hardware.
Howver for businesses RAID, while adding fault tolerance, isn't enough to staisfy business requirements for disaster prevention and recovery. For that, regular scheduled backups are required. Back in the day these were mostly tape, and probably still are for many companies. The advantage of tape is that you can take the tapes off site for secure storage, so if a tidal wave hits the main site the business data can still be retrieved from off-site storage. Tape tends to travel well, unlike disc drives which may be more sensitive to shocks and such. It also can store a lot of data. The drawback of tape is that it's a linear format and ill suited for random retrieval of data. It also tends to be slower in playback than disc drives. I imagine optical discs (DVD and Blu-Ray have stepped in and can perform limited backup functions for smaller amounts of data. In some cases backup drive arrays are located off site and then data is backed up across a secure link. Lots of options there.
Back when I worked in the IT field, it was often a difficult task to convince a small business or department of the need to back up their disk drives to tape. But after one loss of vital business data to a disc drive crash, they suddenly became converts and all ears for any sort of disaster prevention recovery recommendations. Funny how it works that way. Probably still does.
Me? I back up my book keeping software data files at home regularly. The rest? Don't ask

... But then I'm not running a business here.