ZFS pool with 4k sector size

[Michael BlackHeart]

Hello,
I'd like to know what is the best way to convert my pool from 512b sector
size to 4k sector size.

Hardware: 2 x2Tb WD Green with 4k physical sector size

Model Family: Western Digital Caviar Green (AF, SATA 6Gb/s)
Device Model: WDC WD20EARX-00PASB0
Serial Number: WD-WCAZA8280575
LU WWN Device Id: 5 0014ee 206032063
Firmware Version: 51.0AB51
User Capacity: 2 000 398 934 016 bytes [2,00 TB]
Sector Sizes: 512 bytes logical, 4096 bytes physical
Device is: In smartctl database [for details use: -P show]
ATA Version is: ATA8-ACS (minor revision not indicated)
SATA Version is: SATA 3.0, 3.0 Gb/s (current: 3.0 Gb/s)
Local Time is: Thu Aug 22 11:33:16 2013 MSK
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

They're running in a mirror

pool: storage
state: ONLINE
scan: resilvered 48K in 0h0m with 0 errors on Thu Jul 25 19:18:01 2013
config:

NAME STATE READ WRITE CKSUM
storage ONLINE 0 0 0
mirror-0 ONLINE 0 0 0
ada3 ONLINE 0 0 0
ada7 ONLINE 0 0 0

zdb info

storage:
version: 5000
name: 'storage'
state: 0
txg: 1292269
pool_guid: 18442220950447532371
hostid: 708219113
hostname: 'diablo.miekoff.local'
vdev_children: 1
vdev_tree:
type: 'root'
id: 0
guid: 18442220950447532371
create_txg: 4
children[0]:
type: 'mirror'
id: 0
guid: 4289294206539029185
metaslab_array: 33
metaslab_shift: 34
ashift: 9
asize: 2000394125312
is_log: 0
create_txg: 4
children[0]:
type: 'disk'
id: 0
guid: 16348588566764560218
path: '/dev/ada3'
phys_path: '/dev/ada3'
whole_disk: 1
DTL: 95
create_txg: 4
children[1]:
type: 'disk'
id: 1
guid: 7655198429866445090
path: '/dev/ada7'
phys_path: '/dev/ada7'
whole_disk: 1
DTL: 97
create_txg: 4
features_for_read:

As you see ashift is 9 (512b).

I know a common solution with gnop and export-mport pool, but how should I
manage mirror this way? Should I create a mirror on gnop-ed devices and
then export-import?