I attempted to upgrade my FreeNAS Mini from 9.3 to 9.10 and upon reboot, I got errors. i was told to look at /data/update.failed, which I did and have included below. I do not understand what the problem is or how to fix.
This bug will be fixed in the next SU: https://bugs.freenas.org/issues/14602. In the meantime, you should be able to reboot and select the boot environment from before the failed upgrade.