I would consider Linux ZFS only for toy databases that do not hold any serious data.
I call bullshit. I have used ZFS with better performance and it offers higher degree of management of the system.
I look at one articles you pointed out and it was using RAIDZ2 — well there you go. I would not recommend using anything other than RAID10 i.e. stripe of mirrors.
If you’re using RAIDZ# then performance is going to be heavily impacted and I would highlyrecommendNOT using RAIDZ# for a database server.