[OpenIndiana-discuss] zpool import sees nothing after detaching mirror

[solarg]

hello all,
in my Ultra 20, the 2 disks are mirrored with zfs. I detached them, to 
install a new release of the first disk, and keeping the second disk to 
access old datasets.
         rpool         ONLINE
           mirror-0    ONLINE
             c4t1d0s0  ONLINE
             c4t0d0s0  ONLINE
root at openindiana:/jack# #zpool detach rpool c4t1d0s0

But after that, the zpool doesn't show the second disk when doing import!
Is it normal? Is there a way to force it? i also tried with -D argument. 
I did nothing on the second disk, so the bits are always here.

thanks in advance for help,

gerard