I've been reading that some people are installing three hard drives: a small 100 GB drive that boots up and has the OS and programs; one large 1TB drive for a scratch or pagefile disk; and another large 1TB for storage.
And the latter two large drives are RAID0.
(I hope I got all that correct...)
I'm wondering if all this is REALLY worth it?
Does it really help optimize video editing and 3D rendering significantly, compared to say doing it all on one drive like majority of people?
Hard drives seem to be cheap now, and I'm planning a build, but undecided on such a drive setup... is it worth it or a waste of money?
I can't tell you exactly, but those are the types of apps that would have some benefit from doing things to optimize HD usage. I've seen people mention that for things like boot time of gaming, where there's little benefit.
I'm not sure a separate HD for your swap file is that important. More important probably that you have enough RAM that paging is minimized.
RAID 0 will speed up your transfer rates by a good bit, so it could be good for video editing. Due to the decreased reliability of RAID 0, you would need a good backup drive or alternate storage location for your more permanent files though.
Is it worth it? That's a personal question - you're going to spend more money, do you value your time more than the extra hundred bucks or so you spend for an extra HD or 2?