get into single user mode from ok prompt by using the command below.

boot -s

use the newfs command to check the number of back ups for the superblock used.

use newfs -N to display the value for /dev/dsk/c1t1d0s0 as below.

newfs -N /dev/dsk/c1t1d0s0

use fsck command to fix the superblocks as below

fsck -F ufs -o b=75680 /dev/rdsk/c1t1d0s0

Now the blocks are replaced get to multiuser mode using init 3

server should boot fine.