Simple mirror / bootmanager

[Guy Van Sanden]

Hello guys

How can I install the bootmanager to a disk?
The disk is ad1 (primary slave) and is only intended to be booted when
the first disk is removed (so becoming ad0 at that point).
It should be immediately bootable when made primary (e.g. in another
machine)

What I want to do is this.
I have two disk of the same size (give or take a couple of kilobytes),
but with a different geometry.

Only the first disk is used (contains separate / swap /var /tmp /usr
/home /data).

What I want to do is use the second disk as a mirror by creating the
same slice layout, tarring the contents of the original disk and
rsyncing them to the second disk once a day.  If my first disk fails, I
can simply put the second disk as master or even put it in another
machine until the server is rebuilt. 
I don't want to use software mirroring (with vinum), because of the
performance hit and complexity.

I can do all of this, but I don't know how to get the bootmanager on it.

The system is FreeBSD 5.0-RELEASE on A PII-333 with two 40 GB disks.

Thanks for any help.