[volunteers] Re-designed RAID array (was: Out until Thursday Evening)

[Rick Moen]

Quoting Paul Reiber (reiber at gmail.com):

> Rick - if you're still flush w/ time for fun svlug projects :-) I'd
> love some help getting that SCSI raid array reconfigured per your
> recommendations.
> 
> I've cut-n-pasted the history from the original session where we
> created the RAID10 array.
> 
> Can you help me construct the right set of commands to
> convert that mess into what it should be now?

Er, sorry to say, I have almost zero experience with the mdadm utility, 
so I'm a bit at sea about details of its proper use.  Literally the only
time I've created an "md" driver array, I used the Debian "etch" 4.0
installer to do it, rather than wielding mdadm from the command line.
(I _do_ have a lot of experience with RAID at a prior firm, but it was
always hardware RAID.)

So, any "recipe" I attempt to conjure out of thin air is extremely
likely to be missing some essential steps, among other things.  For
example, can I just ignore what's currently on the drives and do "mdadm -C"
to create fresh array data?  I have no idea (though I do suspect one can).

I'm unclear on how many good drives are now in the VA Linux model 9008
JBOD (but you would know).  For purposes of this mail, let's assume 8,
and that we're creating a single 6-drive RAID array with 2 spare drives.
I'll assume that /dev/sda through /dev/sdh each have a single partition
taking up the whole drive, having partition type "fd" (Linux raid
autodetect).

# mknod /dev/sdh1 b 8 113  ## You already did this step.
# mdadm --create --verbose /dev/md0 --level=5 --raid-devices=6 --spare-devices=2 --chunk=256 /dev/sd[a-h]1
# mdadm --detail --scan >> /etc/mdadm/mdadm.conf
# mkfs.ext3 -b 4096 -R stride=8 /dev/md0 

Then, create a mountpoint (/media/jbod, or whatever), mount it, and add
an appropriate line for /dev/md0 to /etc/fstab.  

But I should stress that I really don't know what I'm doing, so the
above may have some holes in it.  I'm guesstimating that it's basically
right, though.

-- 
Cheers,             
Rick Moen                 "Anger makes dull men witty, but it keeps them poor."
rick at linuxmafia.com                                   -- Elizabeth Tudor