mounting raid5 with different unit values

[Raz <raziebe@xxxxxxxxx>]

Hello
I am trying to mount xfs over raid5. I am trying to mount it with
different values than
the true ones. the mount fails with a general error of :
mount -osunit=6144,swidth=18432 /dev/md1 /d1/
mount: wrong fs type, bad option, bad superblock on /dev/md1,
       or too many mounted file systems

the true values are:
xfs_info /d1/
meta-data=/dev/md1               isize=256    agcount=32, agsize=5687296 blks
         =                       sectsz=4096  attr=0
data     =                       bsize=4096   blocks=181989888, imaxpct=25
         =                       sunit=256    swidth=768 blks, unwritten=1
naming   =version 2              bsize=4096
log      =internal               bsize=4096   blocks=32768, version=2
         =                       sectsz=4096  sunit=1 blks
realtime =none                   extsz=3145728 blocks=0, rtextents=0


this same command did work on 2.6.15  while it failing on 2.6.17 .
why ?
-- 
Raz