If the individual drives are too small to run a node, I can see why combining them in a RAID may be the better option. If you’re doing that though, I definitely recommend adding some redundancy. Depending on how many disks you have RAID6 would be preferred, but with 6 or fewer I’d say RAID5 is acceptable. It’s all or nothing with this setup though. If you lose data, your entire node is gone.
The reason I would normally recommend running separate nodes is because you make MORE money until the first HDD failure. After that you make the same amount of money as you would have with a RAID setup. Basically, a failure only makes you lose your added income to begin with. But if your HDD’s individually aren’t large enough, you have little choice but to use RAID.
I absolutely disagree that RAID is a must as @Odmin’s page suggests. In fact in most cases it’s a worse option. We can argue about the better approach, but saying it’s a must is just plain false.
Edit: I went into the details of this a while back in the following post