Comment # 18 on bug 1229020 from Louis Erickson

Some googling has found my problem, and I have resolved it:

zfs had multiple versions installed so the command line tools didn't match the
kernel module, and could not find symbols.  Did not work well.

Uninstalled all ZFS rpm files, and reinstalled from the filesystem repo.

Then the pool would not mount because it thought it had been mounted by another
system.  One with the same name, but a new ID.  A -f to zpool got that sorted,
and suddenly everything worked.

After that, it all worked past a reboot, and all is well.

Thank you again, and we're really done now.  :)