> Which is going to hurt since ZFS with buying everything up front is VASTLY more expensive than RAID where you can grow the array as needed - under the assumpt

> Which is going to hurt since ZFS with buying everything up front is VASTLY more expensive than RAID where you can grow the array as needed - under the assumption that the storage needs grow slowly, which they typically do for home users. Not with mirrored vdevs, which you can expand pair by pair. I'm not arguing for the article, just pointing out your error. The article is very flawed and is bad advice. Not because it's bad per se, but the reasoning fails at basic mathematical analysis. There certainly are valid reasons to use mirrored vdevs. One might be, so you can more easily expand your pool incrementally. Anyway, from personal experience, my thought is that home users should give up on the idea of "incremental expansion" anyway. Double up each time. I'm surprised that you want to say home users aren't going to use 8 drive setups, while at the same time decrying mirrors in favor of parity. If you have a low drive count, the storage efficiency of parity puts you close to that of mirrors anyway. raidz2 with 4 drives as you suggest makes almost no sense vs mirrors.