freebsd-update from 10.1 to 10.2 ZFS trouble

[Denulis]

Hi! I'm upgrading my system from 10.1-RELEASE to 10.2-RELEASE using freebsd-update(8).
I have a ZFS mirror.

10.1

zpool list -v
NAME  SIZE  ALLOC  FREE  FRAG  EXPANDSZ  CAP  DEDUP  HEALTH  ALTROOT
zroot  452G  95.3G  357G  10%  -  21%  1.00x  ONLINE  -
  mirror  452G  95.3G  357G  10%  -
  gpt/zfs0  -  -  -  -  -
  gpt/zfs1  -  -  -  -  -

zpool import
  pool: zroot
  id: 3765752012835992895
  state: UNAVAIL
status: One or more devices are missing from the system.
action: The pool cannot be imported. Attach the missing
   devices and try again.
  see: [URL]http://illumos.org/msg/ZFS-8000-3C[/URL]
config:

   zroot  UNAVAIL  insufficient replicas
    mirror-0  UNAVAIL  insufficient replicas
    14747210912222172309  UNAVAIL  cannot open
    12782398794481350101  UNAVAIL  cannot open

After upgrade to 10.2-RELEASE and rebooting, system doesn't mount the ZFS pool.

Trying to mount root from zfs:zroot/ROOT/default
Mounting from zfs:zroot/ROOT/default failed with error 2: unknown file system.

Booting from LiveCD 10.2, zpool import -f R "id pool" (two pool the same name "zroot"), mount OK. Rename zpool to zroot1 and edit loader.conf vfs.root.mounfrom="zfs:zroot1", and reboot, same error

Booting from LiveCD 10.1, zpool import -f -R /tmp/zroot zroot1, remove /tmp/zroot/boot/kernel and copy kernel file from CD 10.1-RELEASE cp -R /boot/kernel/* /tmp/zroot/boot/kernel. Reboot and zpool good mount.

WTF?