turn into mirror

In below example i've used single volume zfs pool to convert it into mirror zpool.
To show the possibilities of zfs in more extensive way it's based on file volumes instead of drives.

# mkfile -nv 1g mud
mud 1073741824 bytes
# zpool create pond /export/mud

I've created the pond pool based on a mud file.
Now, using the attach method of zpool command, I'll turn it into mirror with water (second file volume).

# mkfile -nv 1g water
water 1073741824 bytes
# zpool attach pond /export/mud /export/water
# zpool status pond
  pool: pond
 state: ONLINE
 scrub: resilver completed with 0 errors on Wed Apr 11 09:43:22 2007
config:

        NAME               STATE     READ WRITE CKSUM
        pond               ONLINE       0     0     0
          mirror           ONLINE       0     0     0
            /export/mud    ONLINE       0     0     0
            /export/water  ONLINE       0     0     0

errors: No known data errors