In this example, you would determine the path to the alternate boot device by using the ls -l command on the slice that is being attached as the second submirror to the root (/) mirror.
# ls -l /dev/dsk/c1t0d0s0 lrwxrwxrwx 1 root root 55 Mar 5 12:54 /dev/rdsk/c1t0d0s0 -> ../. ./devices/eisa/eha@1000,0/cmdk@1,0:a |
Here, you would record the string that follows the /devices directory: /eisa/eha@1000,0/cmdk@1,0:a