10.0-BETA4 (upgraded from 9.2-RELEASE) zpool upgrade -> boot failure

[Artem Belevich]

On Thu, Dec 12, 2013 at 4:28 AM, Andriy Gapon <avg at freebsd.org> wrote:
>> Yes, sorry. You can find here the script I use to install:
>>
>> https://github.com/Leryan/freebsd-zfs-install/blob/master/zfs.sh
>>

>From zfs.sh:
># Zero ZFS sectors
>dd if=/dev/zero of=/dev/${ada}p3 count=560 bs=512

That destroys only half of ZFS uberblocks. The other half is placed at
the top of the vdev slices in the pool.
There were few reports recently that such 'orphan' ZFS uberblocks were
messing up boot on recent FreeBSD versions.

Considering lack of details on how exactly your boot fails, this may
or may not be the issue in your case.

do  "zdb -l /dev/ada0" (and all other slices on ada0) and check
whether it reports anything unexpected.

--Artem