errors using newfs

Hi,

I am trying to create a new file system on solaris 10.  Can someone help me in understanding why I am getting this error?

# newfs -Nv /dev/rdsk/c2t21d133s2

pfexec mkfs -F ufs -o N /dev/rdsk/c2t21d133s2 20963328 256 -1 8192 1024 220 1 250 8192 t 0 -1 8 16 n

/dev/rdsk/c2t21d133s2:  20963328 sectors in 3412 cylinders of 48 tracks, 128 sectors

        10236.0MB in 214 cyl groups (16 c/g, 48.00MB/g, 5824 i/g)

/dev/rdsk/c2t21d133s2:  20963328 sectors in 5118 cylinders of 16 tracks, 256 sectors

        10236.0MB in 197 cyl groups (26 c/g, 52.00MB/g, 6400 i/g)

Error determining alternate superblock locations

I know the -N is just for testing which is what I want to do first.  I don't understand why I see error in determining the alternat superblocks.