cvs commit: src/sys/geom geom_fox.c src/sys/modules/geomMakefile src/sys/modules/geom/geom_fox Makefile src/sys/conf NOTES files options

[Nate Lawson]

On Wed, 18 Jun 2003, Poul-Henning Kamp wrote:
>   Add "GEOM_FOX", a class which detects and selects between multiple
>   redundant paths to the same device.
>
>   This class reacts to a label in the first sector of the device,
>   which is created the following way:
>
>           #    "0123456789abcdef012345..."
>           #    "<----magic-----><-id-...>
>           echo "GEOM::FOX       someid" | dd of=/dev/da0 conv=sync

This looks interesting.  Have you shown this to gordon@ who is adding
something similar to FFS?  It might be good to have a generalized config
tool.

Won't the location you've chosen interfere with an MBR on i386 drives?
Is it possible to pick another space (i.e. FFS label, {bsd,sun}label
fields, GPT)?

>   NB: Since the fact that multiple disk devices are in fact the same
>       device is not known to GEOM, the geom taste/spoil process cannot
>       fully catch all corner cases and this module can therefore be
>       confused if you do the right wrong things.
>
>   NB: The disk level drivers need to do the right thing for this to
>       be useful, and that is not by definition currently the case.

You're right in that it will be a while before disk devices handle
multipathing themselves.  It would be great if you could help with making
device_t support this kind of operation.

-Nate