[clug-talk] RAID resync failure

[Dan Graham]

Hi Ian,

I have seen this happen when you create an mdadm RAID5 array without a
hot spare drive (4th disk). When a drive in the array fails with only
3 disks it cannot rebuild itself without the hot spare. You may be
able to add an additional disk to the array and then try rebuilding it
but it will take far less time to create an entirely new array and
copy your backup data to it.

All the best, Dan

On Fri, Jan 2, 2009 at 4:24 PM, Ian Bruseker <ian.bruseker at gmail.com> wrote:
> Greetings and happy new year to all.  Well, happy new year to all expect my
> RAID that is failing to resync.
> I have a 3 disk RAID 5 array.  Two days ago it was working just fine.
>  Yesterday I transplanted the guts of my computer into a new case that I got
> for Christmas.  On first reboot, no RAID.  Then I realized I had forgotten
> to hook up one of the standalone drives, causing all the sd?'s to shift by
> one, making them not match what is in my mdadm.conf.  Hooked it everything
> as it should be, and the system came up fine.  A little while later the
> system froze.  I don't know why, but it locked up hard.  I am pretty sure
> that it was writing some data on the array partition when this happened
> though, should that be relevant.  When I reset, I noticed that the hard
> drive light was on solid.  Thinking it was an artifact of the hard reset, I
> just did a proper shut down and reboot.  It didn't come back on after that
> reboot, but then the next reboot (unrelated tweaking), it did come back. I
> finally clued in and checked /proc/mdstat, and found my array was
> rebuilding.  Fine, but after a while the computer locked up solid again.
>  After several hours of this happening, and some sleuthing, I've figured out
> that every time my array gets to 40.1% of the resync, it locks the computer
> solid.  Has anyone ever seen anything like this before?  I found a thread in
> the Ubuntu forums here:  http://ubuntuforums.org/showthread.php?t=939923  in
> which the person had the same problem, but they managed to fix it by booting
> from a Knoppix CD.  I tried that, but it did exactly the same thing, locking
> at 40.1%.  I'm getting nothing in the log files that would indicate
> anything, but perhaps it locks up before it has a chance to log the problem.
>  My gut is leading me to it being a bad disk, but I thought I'd ask if
> anyone know any other tricks before I got drop cash on a new drive.
> Thanks,
> Ian
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