As far as I can see, RAID 0 is a way to combine multiple hard disks as one without any redundancy.
Correct. RAID 0 (stripe) has at least two implementations. One of them just appends disks, making multiple disks act as one big drive. One which alternates sectors between drives, allowing up to double performance with two drives.
With a single disk there are very few reasons to use RAID.
That does not mean that you can not set up RAID with a single disk, e.g when:
- You set it up as a mirror with missing second device. (Presumably because you want to add one later and just let things sync without setting up a new configuration).
- You want experiment with disk layouts. (No performance is gained, only complexity is increased).
- Or you want to remain an identical setup with other computer (e.g. with Dell Lattitude E-series laptops which for some reason come with the BIOS set to RAID mode and a single drive. I am not sure what the people smoked before deciding on that. Maybe it was marketing which wanted to be able to use the term RAID).
Having said that, I see no sane reason to use a single disk in RAID mode. Use any modern SSD with the normal AHCI mode. Not in ancient IDE mode, and not in IRST mode.