ZFS i/o error on boot unable to start system

[Vikash Badal (IS)]

Hi James,

On 2020/02/28 15:51, James B. Byrne via freebsd-questions wrote:
> I have reported this on the forums as well.
>
			
Vikash Badal (IS)
Senior Technical Systems Engineer
T +27 11 5750825 


this helped me with this issue:
https://forums.freebsd.org/threads/i-broke-11-0-beta2-uefi-zfs-root-boot.57137/

tldr;

-  boot usb/cd image (must be same version -as OS)

from shell:
- gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 <drive0-n>
-  if you using uefi:
   dd if=/boot/boot1.efifat of=/dev/<drive0-n>p1


refs:
https://solence.de/2019/05/01/update-uefi-boot-code-after-zfs-upgrade-on-freebsd/
https://forums.freebsd.org/threads/i-broke-11-0-beta2-uefi-zfs-root-boot.57137/


> FreeBSD-12.1p2
> raidz2 on 4x8TB HDD (reds)
> root on zfs
> 
> We did a hot restart of this host this morning and received the following on
> the console:
> 
> ZFS: i/o error - all block copies unavailable
> ZFS: failed to read pool zroot directory object
> qptzfsboot: failed to mount default pool zroot
> 
> FreeBSD/x86 boot
> ZFS: i/o error - all block copies unavailable
> ZFS: can't fild dataset 0
> Default: zroot/<0x0>
> boot:
> 
> What has happened?  How do I get this system back up and online?
> 
> My first thought is that in modifying rc.conf to change some ip4 address
> assignments that I may have done something else inadvertently which has caused
> this.  I cannot think of any other changes made since the system was last
> restarted a noon yesterday.
> 
> ​This is an urgent matter.  Any help is gratefully welcomed.
>