> Something I've wonderd about for a while:  why does NetBSD have both
> mfs and a ram-disk driver?   It seems somewhat redundant. Is the 
> ramdisk necessary for booting on some ports?  If so, what's the
> advantage of mfs over an ffs filesystem on a ramdisk?

mfs is effectively a ffs on a ramdisk.  (NO, it does NOT trade memory
back and forth with the VM system.  It allocates a fixed amount of
memory to start up, slowly backs it with pages as needed, and as far
as i know never gives any back.)

mfs has two potential advantages:
	(1) configuration simplicity (easy to use from fstab, etc.)
	(2) potentially optimizable: no reason it _has_ to use ffs
	    structure, that's just easiest.

arguably, mount_mfs could be turned into a wrapper that makes a
ramdisk, newfs's it, and mounts it...  but it's not clear how easily
that could be done to keep the current semantics, and it certainly
wouldn't keep the second advantage listed above.


cgd