Auto Import multi volumes in one disk

[Kelvin Lee]

At first, pls forgive my poor english.

I have a problem like this, I have install a new freenas in the following hardware:
intel i3 cpu
25GB IDE HDD - FOR system
3tb SATA HDD - FOR Storage, i want to make 3 partitions in their, and make the mirror on zfs, and import to freenas.
there is my step:
1. install the freenas
2. use shell to gpart the 3tb SATA HDDs, like this:
[root@freenas ~]# gpart show
=> 34 41942973 ada0 GPT (20G)
34 614400 1 freebsd-zfs (300M)
614434 614400 2 freebsd-zfs (300M)
1228834 40714173 - free - (19G)

=> 34 41942973 ada1 GPT (20G)
34 614400 1 freebsd-zfs (300M)
614434 614400 2 freebsd-zfs (300M)
1228834 40714173 - free - (19G)

=> 63 4194225 ada2 MBR (2.0G)
63 1930257 1 freebsd [active] (943M)
1930320 63 - free - (32K)
1930383 1930257 2 freebsd (943M)
3860640 3024 3 freebsd (1.5M)
3863664 41328 4 freebsd (20M)
3904992 289296 - free - (141M)

=> 0 1930257 ada2s1 BSD (943M)
0 16 - free - (8.0K)
16 1930241 1 !0 (943M)
3. use the zpool to create 3 zfs to mirror it. like this:
pool: test2
state: ONLINE
scrub: none requested
config:

NAME STATE READ WRITE CKSUM
test2 ONLINE 0 0 0
mirror ONLINE 0 0 0
ada0p2 ONLINE 0 0 0
ada1p2 ONLINE 0 0 0

errors: No known data errors
4. export them, to make the freenas can detect it.
5. auto import volume, but after import anyone volume, then i click again auto import volume, their can't list the remain volume in zpool.

Am i got any mistake in step? or something wrong? pls help, thanks a lot.