As the author of that article, thank you. And, I agree it would be sad if you had to think about exactly how many drives are in a RAID-Z group. The entire point of my blog post is that you do not have to think about it.
"TL;DR: Choose a RAID-Z stripe width based on your IOPS needs and the amount of space you are willing to devote to parity information. Trying to optimize your RAID-Z stripe width based on exact numbers is irrelevant in nearly all cases."
ZFS device removal is on its way but not quite in illumos yet. From Alex's blog post: "We’ll publish the code when we ship our next release, probably in March [2015], [and we will] integrate into Illumos once we address all the future work issues."
You don't see Linus's viewpoint as contrary to the one on gnu.org? It seems like Linus is saying that the GPL allows AFS to be used with Linux (because it is not a "derived work"). How is ZFS different from AFS in this respect?
The legal issue is a matter of some debate (see below). In practice, I don't think the Benevolent Dictator wants ZFS in the main Linux kernel tree at the moment.
"TL;DR: Choose a RAID-Z stripe width based on your IOPS needs and the amount of space you are willing to devote to parity information. Trying to optimize your RAID-Z stripe width based on exact numbers is irrelevant in nearly all cases."