> If anything, OpenZFS built upon that by now documenting the previously deeply hidden option to "rewind" ZFS uberblock if the breakage is recent enough.

One of the most "wizardry" moments in my career I've personally witnessed was a deep-level ZFS expert (core OpenZFS developer) we had on retainer come in during a sev0 emergency and rapidly diagnose/rollback a very broken ZFS filesystem to a previous version from a few hours before the incident happened.

This was entirely user error (an admin connected redundant ZFS "heads" to the same JBOD in an incorrect manner so both thought they were primary and both wrote to the disks) that we caught more or less immediately so the damage was somewhat limited. At the time we thought we were screwed and would have to restore from the previous days backup with a multi-day (at best) time to repair.

This was on illumos a few years after the Solaris fork, so I don't think this feature was documented at the time. It certainly was a surprise to me, even though I knew that "in theory" such capability existed. The CLI incantations though were pure wizardry level stuff, especially watching it in real time with terminal sharing with someone who very much knew what they were doing.