I think that this will solve your hunt for informations ;-)
http://www.openbsd.org/papers/asiabsdcon2010_softraid/softraid.pdf

On Sun, Oct 24, 2010 at 1:21 AM, Jean-Francois <jfsimon1981@gmail.com> wrote:
quoted text
> Hi,
>
> I'm having difficulty to understand how softraid works ie. how to add chunks,
> remove chunks, change and rebuild, add/remove hotspares.
>
> The manpages bioctl & softraid only mention basic configuration, but once the
> raid is working ... any other related docs or man ?
>
> Thanks,
>
> J-F