Geom class project idea - geom_cow

[Christian Laursen]

I have an idea for a geom class that I think could be useful in a number
of scenarios.

The basic idea is that it takes two existing providers and uses the first
one as a starting point and the other one to keep changes to the first
one using copy-on-write.

The second provider will need a bitmap to keep track of the blocks that
have changed as well as at least as much space as the base provider.

A number of the cases in which this class would prove useful are cases
where you would otherwise choose unionfs. However, approaching this
problem in geom seems simpler. (At least to me)

I propose that this idea be added to <http://www.freebsd.org/projects/ideas/>
and/or <http://www.freebsd.org/projects/summerofcode.html>.

Unfortunately I don't have the time nor much kernel hacking experience to
do this myself at this point.

-- 
Christian Laursen