What constitutes a subjective question on superuser.com? I'm thinking of a RAID setup and want to throw around ideas, is that too subjective?
"Throwing around ideas" is usually subjective, and usually not a question anyway.
By definition, if a question doesn't have a canonical answer--or at least, a very small set of equally viable answers--then it's really just opinion-polling.
If you can draw a straight line from the question to the answer, then it's a good question. If you need a mind-map to cover the answers, then it's not really a question in the Stack Exchange sense.
If you think about it, you can make anything a question by narrowing it down enough. Granted that yes/no questions are generally bad questions, that still leaves a lot of room to maneuver.
Some made up examples, using your topic, may illustrate.
Will MySQL read performance be better with RAID-6 than RAID-4?
Benchmarking questions are generally bad, but at least this allows one to point to published facts about a given use case.
What's the best RAID level for running a server?
Not enough context. No way to point to any real data. Any answer will be conjecture or opinion, or simply an abstract use case.
Not every problem has an orthogonal solution, but if the set of possible solutions is very large or a matter of personal taste, then it's subjective. Q.E.D.