Geom RAID root report.

[David Gilbert]

Before making this machine, I did a search on the lists to see if
anyone else had questions or was willing to report on using a GEOM
RAID root device.  Nobody had.

So... here's the basic recipe.

First I did a minimal install to one of the two disks in a 512M root.
I think 256M would be enough for that, but the disks are just so
bloody huge.  Anyways... then I booted from the fix-it CD to try to
mirror up the 'a' partition.

Gmirror on the fix-it CD appears to be impotent.  It appears to have
only 'help', 'list', 'load' and 'unload' as commands.  Not useful.

Since I had a few spare disks around, I loaded a default load onto one
and tried again.

The disklabel created by sysinstall had the 'a' pertition starting at
0.  Creating a gmirror starting at the beginning of a disk or ending
at the end seems to break things, and it did here.  Gmirror (the
kernel module) seems to find the provider as the parent (say ad4s1)
instead of the child (ad4s1a).

So I used 'dump' to image 'a' and then I relabeled and repartioned the
disk to start 'a' at block 64.  gmirror on this worked and formatting
it and restoring to it are fine.

Now... you do need to mount this filesystem and edit a few things.

geom_mirror_load=YES

needs to be in /boot/loader.conf

Your fstab will likely need to look like:

# Device                Mountpoint      FStype  Options         Dump    Pass#
/dev/mirror/cs-swap     none            swap    sw              0       0
/dev/mirror/cs-root     /               ufs     rw              1       1
/dev/mirror/cs-var      /var            ufs     rw              2       2
/dev/mirror/cs-usr      /usr            ufs     rw              2       2

... obviously substituting your own geom mirror names.

Note that using a geom swap requires

swapoff="YES"

in /etc/rc.conf

But otherwise, this all seems to work ... even without the nasty
recalculation of the fake 'a' partition required by vinum.

Dave.

-- 
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|David Gilbert, Independent Contractor.       | Two things can only be     |
|Mail:       dave at daveg.ca                    |  equal if and only if they |
|http://daveg.ca                              |   are precisely opposite.  |
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