Do you know of any OS that would put the superblock in sector 0?
I googled a bit, but I couldn't find examples where UFS would
not start with a boot sector (afaics, it usually starts with a
bootblock area of at least 8KiB -- with OS-specific data in it,
e.g. a disklabel).
According to *BSD http://fxr.watson.org/fxr/source/ufs/ffs/fs.h:
*/"* Depending on the architecture and the media, the superblock may/*
*/* reside in any one of four places. For tiny media where every block /*
*/* counts, it is placed at the very front of the partition. Historically,/*
*/* UFS1 placed it 8K from the front to leave room for the disk label and/*
*/* a small bootstrap. For UFS2 it got moved to 64K from the front to leave/*
*/* room for the disk label and a bigger bootstrap, and for really piggy/*
*/* systems we check at 256K from the front if the first three fail/*"