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*
In message <[EMAIL PROTECTED]>, Poul-Henning Kamp w
rites:
>phk 2003/06/18 02:29:28 PDT
>
> FreeBSD src repository
>
> Modified files:
> sys/modules/geom Makefile
> sys/conf NOTES files options
> Added files:
> sys/geom geom_fox.c
> sys/modules/geom/geom_fox Makefile
> Log:
> 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
>
> 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.
>
> Revision Changes Path
> 1.1153 +1 -0 src/sys/conf/NOTES
> 1.795 +1 -0 src/sys/conf/files
> 1.395 +1 -0 src/sys/conf/options
> 1.1 +468 -0 src/sys/geom/geom_fox.c (new)
> 1.4 +1 -0 src/sys/modules/geom/Makefile
> 1.1 +8 -0 src/sys/modules/geom/geom_fox/Makefile (new)
>
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
[EMAIL PROTECTED] | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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