[Yaffs] umounting yaffs rootfs

             I have a yaffs based root filesystem which works
perfectly. The concern is that if i am using yaffs as the rootfs ,
poweroff/halt/reboot wont umount the
rootfs and says it is busy. After the reboot this unclean reboot adds
a 8 second delay mounting the yaffs rootfs. On the other hand if i
boot into an alternate rootfs , mount original yaffs rootfs , umount
original yaffs rootfs and reboot into the  original rootfs then i dont
see the 8 second delay . I assume this is because of checkpointing ?
How can i avoid this 8 seconds delay ? Is using a initrd the only way
to be able to cleanly umount the yaffs partition? Is umounting very
critical ? Please shed some pointers on how to efficiently use yaffs
as a rootfs.