Parity? Three-way mirror?

I chose this question due to the numbers of answers, possible complications and questions concerning labeling again. Does mirroring using parity data? Im honestly not sure but I think its a safe assumption that if you are using a space saving raid configuration
some semblance of parity data must be in use. Thus its either the right answer or just listed as an option to throw nubs off.

Anyway here is the question/answer set:

So as you can see parity is there but I think the understanding is that its an incomplete answer. Which begs the question what exactly is a three-way mirror? You have 3 sets of disks and all three have the same set of data on them? Im unfamiliar with this idea in the
context of raid configurations. I guess it does say if two disks fail at the same time, so that actually makes sense and this is here to explain but it still doesn’t explain why that you would use 5 disks in this situation. If your using less disk than a 1 to 1 ratio (or more in this case) what’s going on with the extra disks in this raid configuration?

As you can read in msft linked article you can see that the word parity is even mentioned and the answer doesn’t provide for much in the way of clarity. Not much to do here but assume that super obscure ideas are fair game.

Any way, if I was feeling more spunky or had more time I would link to articles on each of the answers but that isn’t exactly what im going for with this set or what I have the time to do, at this point.