Greg A. Woods writes:

> Then for the real test start over and do it all again, but this time
> after "systat bufcache" shows that most of available RAM is used up
> for metadata an file data, pull the power plugs.  Then try to clean
> up the mess.

What mess?  My understanding is that with soft updates, the only
thing that can possibly happen is that disk space can be lost.
The background fsck is for reclaiming this lost space.