Quick ZFS mirroring question for non-mirrored pool

[Kaya Saman]

Hi,

I'm just exploring ZFS commands currently as I haven't used much of ZFS 
even though I deal with BSD and Solaris/OpenSolaris on a daily basis.....

Basically what I am about to do is build a new server using FreeBSD 8.0 
x64 on a Mini-ITX system and unfortunately due to budget I won't be able 
to get the extra 2 disks that I need so out of 4 disks overall is 2.

I just really wanted to ask after using these tutorials:

http://wiki.freebsd.org/ZFSQuickStartGuide

http://blog.thefrog.net/2008/04/zfs-on-freebsd.html

http://flux.org.uk/howto/solaris/zfs_tutorial_01

if it's possible to add a mirror to a non-mirrored pool??

It's a bit hard to explain but taken from the last URL:

I created 4 files using mkfile in /mnt called file1...4

Now I added the first 2 to a pool: zpool create zpool1 /mnt/disk1 /mnt/disk2

and checked the status:

zpool status zpool1
   pool: zpool1
  state: ONLINE
  scrub: none requested
config:

     NAME          STATE     READ WRITE CKSUM
     zpool1        ONLINE       0     0     0
       /mnt/disk1  ONLINE       0     0     0
       /mnt/disk2  ONLINE       0     0     0

errors: No known data errors


What I would like to do over time is add 2 more disks to this pool (in 
real life, however for my demo they will be /mnt/disk3 and /mnt/disk4). 
The real catch is that I would like disks 3 + 4 to be a mirror of the 
first 2 disks.....

Is this possible to start with without loosing any data and destroying 
the pool?

Or do I need to create another pool say zpool2 and mirror the pools??

So in RAID terms I guess would be something like disk1 and 2 in RAID 0 
with disks 3 + 4 in RAID 0 however, RAID0(1) in RAID 1 array with 
RAID0(2).....

Perhaps is RAID 1+ 0 which I'm trying to achieve I don't know but 
currently I'm not really getting anywhere with what I've tried and 
managed to crash the kernel and make the system reboot already.

 From scratch it would be so easy as I could just use: zpool create 
zpool1 mirror /mnt/disk1 /mnt/disk2 mirror /mnt/disk3 /mnt/disk4.

Can anyone give me any advice??

Many thanks,

Kaya