Date: Wed, 18 Jun 2003 12:53:52 -0700 (PDT) From: Nate Lawson <nate@root.org> To: Poul-Henning Kamp <phk@FreeBSD.org> Cc: cvs-all@FreeBSD.org Subject: Re: 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 Message-ID: <20030618125009.K56972@root.org> In-Reply-To: <20030618092938.2E5FC37B418@hub.freebsd.org> References: <20030618092938.2E5FC37B418@hub.freebsd.org>
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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
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