Live Upgrade - unable to create a new BE because the second is already in use by another BE

Hi experts,

I'm doing a live upgrade on a SPARC server. there are two disks on this server mirrored using SVM. I detached all slices of c1t2d0 from metadevice:

bash-3.2# df -hF ufs
Filesystem             size   used  avail capacity  Mounted on
/dev/md/dsk/d0         9.8G   3.3G   6.4G    35%    /
/dev/md/dsk/d3          28G    18G   9.2G    67%    /var
/dev/md/dsk/d4         9.8G   5.9G   3.9G    61%    /opt
/dev/dsk/c1t0d0s0       67G    10G    56G    16%    /opt/apps/splunk
/dev/md/dsk/d6         3.9G   486M   3.4G    13%    /var/bns/audit

bash-3.2# metastat -cp
d4               m   10GB d24
    d24          s   10GB c1t1d0s4