mount root rw in amd64 not working

[billm]

I was able to mount the root rw in i386, but I'm not able to do it since I upgraded to amd64. At least I think that's the cause of the problem
I use "mount -uw /". I get no error message, but after that, if I run mount by its self I get
/dev/ufs/FreeNASs2a on / (ufs, local, read-only, soft-updates)
devfs on /dev (devfs, local, multilabel)
/dev/md0 on /etc (ufs, local)
/dev/md1 on /mnt (ufs, local)
/dev/md2 on /var (ufs, local)
/dev/ufs/FreeNASs4 on /data (ufs, local, soft-updates)

I want to edit the /boot/loader.conf file to add "vfs.zfs.prefetch_disable=0"

Thanks!