Re: RAID MIA. Again. (Kinda.)

[Neil Brown <neilb@suse.de>]

On Thu, 4 Mar 2010 17:00:10 -0500 (EST)
"Ken D'Ambrosio" <ken@jots.org> wrote:

> On Thu, March 4, 2010 3:50 pm, Neil Brown wrote:
> > On Thu, 4 Mar 2010 11:12:29 -0500 (EST)
> > "Ken D'Ambrosio" <ken@jots.org> wrote:
> 
> [bad things happened to Ken's RAID-5 here]
> 
> >
> > You missed the bit where you provide concrete information rather than
> > vaguaries.
> 
> Humble apologies; I'm not well-enough versed with the intricacies of Linux
> RAID to know what's appropriate and not.
> 
> > I'm guessing that you created the array over whole-devices, and then
> > partitioned the array - is that correct? If fdisk shows you an
> > unpartitioned array, maybe just the partition table is corrupt.   Seems
> > strange.
> 
> Actually, no.  These were created using /dev/sd[abcd]2 -- I saved off
> space on sd[abcd]1 for swap, /tmp, etc.  Done via the Ubuntu installer, if
> that makes a difference.  For the record, all the /dev/sd[abcd]1 non-RAID
> partitions look fine.
> 
> > To so that I/we don't have to guess, please give exact commands that you
> > run and the exact output so we have access to the same information as you.
> 
> Well, I rebooted, and was surprised that nothing RAID-esque came up. 
> Since my OS is on one of the afore-mentioned non-RAIDed partitions, the
> OS, itself, booted, but none of the RAID partitions mounted.  I tried to
> mount, and failed.  That's when I checked the RAID device, /dev/md0. 
> fdisk showed it lacking any partitions, but the mdadm.conf file hadn't
> been touched for a couple of weeks, so I was pretty sure nothing there had
> changed.  On the off chance that the SCSI drives had re-ordered
> themselves, I went through all 24 permutations of
> mdadm --assemble /dev/md0 /dev/sda2 /dev/sdb2 /dev/sdc2 /dev/sdd2
> since I wasn't sure if the drive order was significant.  All of them
> "worked," inasmuch as they created /dev/md0, but in all cases it was
> partitionless.  I also tried mdadm --detail --scan, to verify that it
> matched UUIDs with those in the /etc/mdadm.conf file, and it did (the
> array line looks thusly:
> ARRAY /dev/md0 level=raid5 num-devices=4
> UUID=1e89645a:7e24dcef:9e77d54f:077a6a6f  )
> 
> 
> > Too much data is much much better than not enough.
> 
> Granted... but, sometimes -- especially when learning -- there can be a
> bad signal:noise ratio.  Tends to make me hesitant when I'm a (relative)
> newbie to a given topic.  That being said, I *think* I've figured out what
> I should be doing, but I also think I did it.  Did I miss something?

Which part of "please give exact commands that you
run and the exact output"
Did you have trouble with?

Try this:

cat /etc/fstab
cat /etc/mdadm.conf
mdadm -Esvv
mdadm -Asv
blkid -p /dev/md*

And include all the output.

(sorry if I seem grumpy, but I'm a bit tired which makes it harder to appear
polite).

NeilBrown