ZFS i/o error in recent 12.0

[Thomas Steen Rasmussen]

On 03/20/2018 12:00 AM, KIRIYAMA Kazuhiko wrote:
> Hi,
>
> I've been encountered suddenly death in ZFS full volume
> machine(r330434) about 10 days after installation[1]:
>
> ZFS: i/o error - all block copies unavailable
> ZFS: can't read MOS of pool zroot
> gptzfsboot: failed to mount default pool zroot
>
> FreeBSD/x86 boot
> ZFS: i/o error - all block copies unavailable
> ZFS: can't find dataset u
> Default: zroot/<0x0>:
> boot: 

Has this pool had new vdevs addded to it since the server was installed?
What does a "zpool status" look like when the pool is imported?

/Thomas