And, yeah, the “smartctl -a /dev/sd” output was SUPER cryptic. This was for /dev/sda, I think, but they all gave nearly identical outputs. Nothing jumped out at me.
However, “smartctl -t short /dev/sd” gave MUCH clearer feedback, and every disk showed as passing, no failures. Here’s my output from that: Zero smart errors.
In all of the reading I’ve been doing over the last ~2.5 days, it seems more and more likely that there’s something broken in the zpool import or zfs filesystem headers or SOMETHING that’s causing this stupid stuff to happen. I just can’t diagnose or resolve it for the life of me.