4.x device failure?

[Poul-Henning Kamp]

In message <Pine.LNX.4.60.0409131505220.6275 at athena>, Sam writes:
>Ah.  Well that answers it.  I'll fail unloading of the
>module if devices are open.
>
>This leads to a curiosity as to how the RAID
>failover modules work at all.  I guess if you abstract
>the real disk(s) under a logical disk you can change
>the bottom layer without affecting the top.  I'll have
>to look at that code a little closer.

You should really start to study GEOM in 5.x which gives a nice
clean framework for all this sort of stuff.

You can start here for instance:

	http://phk.freebsd.dk/pubs/bsdcan-04.slides.geomtut.pdf

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