Handbook mirroring section

[Warren Block]

On Tue, 5 Jun 2012, Hiroki Sato wrote:

> Warren Block <wblock at wonkity.com> wrote
>  in <alpine.BSF.2.00.1206041331520.945 at wonkity.com>:
>
> wb> It's a little tricky.  What do you think about having two sections,
> wb> one for how to create a standard mirror from scratch, and one for
> wb> converting a single-disk system to a mirror?
>
> It sounds like a good idea.

Here's a pass at it:

http://www.wonkity.com/~wblock/mirror/book.html
http://www.wonkity.com/~wblock/mirror/patch-geom-2.diff

Notes:

I tried to factor out common information to the introduction and 
the Troubleshooting section afterward.

diskinfo(8) was used in place of gpart list because the disk capacity is 
in the first three lines, so the command line is simpler.

There is no entity for gnop(8) yet, but I have one locally.