GEOM_FOX?

[Eric Anderson]

What's the status on GEOM_FOX?  This is very interesting to me, as I 
have a lot of fiber channel/SAN backend now, and would like to utilize 
multiple paths with FreeBSD.

Eric


Here's a note I found from phk@:
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I have just committed the GEOM_FOX class, see commit message below.

GEOM_FOX is named after the common red fox, which amongst other
traits have a liking for having multiple exits from its den.

GEOM_FOX will recognize a magic label on the device, and all devices
which come up with the same label will be assumed to be independent
paths to the same underlying physical device.

The first device found will name the created redundant device (I
need to work on that aspect because it makes the name a bit
unpredicatable right now).

If the currently used path to the device fails, GEOM_FOX will switch
to another path and retry the operation.

For anyone who wants to play with this, the following shell script
could be a beginning.  It exploits the fact that the same file can
be used to back several MD(4) devices, so you need no special
hardware.

This will probably be most interesting for people with FibreChannel/SAN
hardware, but since the isp driver has very aggresive retrie policies
as it is now, the actual usability is still somewhat below par.
I'm sure both mjacob an I would appreciate any help we can get in
fixing this.


	#!/bin/sh

	set -ex

	# cleanup
	mdconfig -d -u 10 > /dev/null 2>&1 || true
	mdconfig -d -u 20 > /dev/null 2>&1 || true
	kldunload geom_fox > /dev/null 2>&1 || true

	# Create a 4M disk image
	dd if=/dev/zero of=fox.img bs=1k count=4096

	# create a "disk" on it.
	mdconfig -a -t vnode -f fox.img -u 10

	# Put the GEOM::FOX label on it
	echo "GEOM::FOX       test-fox" | dd of=/dev/md10 conv=sync

	# load the geom_fox module
	kldload geom_fox

	# add another path
	mdconfig -a -t vnode -f fox.img -u 20

	# remove it again
	mdconfig -d -u 20

	# add it again
	mdconfig -a -t vnode -f fox.img -u 20

	# remove the original path
	mdconfig -d -u 10

	# add it again
	mdconfig -a -t vnode -f fox.img -u 10

	# newfs the "fox"
	newfs /dev/md10.fox

	# fsck it
	fsck_ffs /dev/md10.fox

	# remove the currently primary path
	mdconfig -d -u 20

	# fsck it again
	fsck_ffs /dev/md10.fox

	# add a new secondary path
	mdconfig -a -t vnode -f fox.img -u 30

	# remove the primary
	mdconfig -d -u 10

	# fsck it again
	fsck_ffs /dev/md10.fox

	# Remove the primary and only path
	mdconfig -d -u 30

	# See what's left (hopefully nothing)
	ls -l /dev/md*

-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
Anything that works is better than anything that doesn't.
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