zfs discuss - Dec 2007 - Same device added twice

Hi,

I''m new to the list and fairly new to ZFS so hopefully this
isn''t a dumb
question, but...

I just inadvertantly added s0 of a disk to a zpool, and then added the 
entire device:

NAME                                       STATE     READ WRITE CKSUM
zfs-bo                                     ONLINE       0     0     0
c4t60060E801419DC00000119DC000001A0d0    ONLINE       0     0     0
c4t600A0B800026A5EC000007FE47557497d0s0  ONLINE       0     0     0
c4t600A0B800026A5EC000007FE47557497d0    ONLINE       0     0     0

This stirkes me as bad - should I be able to do this?

Thanks,

Tony