Regarding #2: On OpenIndiana, we first started with concurrent zfs commands and ruin, I think, the whole pool (maybe it wasn't that drastic, but was still a disaster scenario where key data would be lost). I couldn't believe it.

I was asking anyone who knew anything... 'so if two admins were logged in at the same time and made two zvols, they could basically ruin their filesystem'? No one knew for sure. Crazy stuff.

Anyway, I'm quite glad that's safe now.