But now I'm staring down the barrel of building a new box for holding a lot of media files, and suddenly, the notion of being able to expand your RAID5 array started to sound important–especially when the case I initially intend to use won't hold more than 3 drives, but I would like to be able to expand later.
As is almost always the case in the geek community, someone has documented their experiences doing just this. Its sounds extraordinarily painless. Even resizing the filesystem on-line was a no-brainer.
So, the related question is whether or not the Areca hardware-raid card I have laying around is actually capable of doing this–the data sheet suggests that it'll even convert, say, a mirrored drive pair to RAID5, but that mildly strains my credulity. I may have to actually, shudder, experiment.