[mdlug] "Device busy" errors and RAID setup issues

[Jeff Hanson]

On Mon, Nov 9, 2009 at 8:09 PM, David McMillan <skyefire at skyefire.org> wrote:
>
>        Not sure what I have going on here.  I've built myself a (intended)
> RAID server with five SATA 1TB drives dedicated to the RAID array
> (separate dedicated boot drive), running Jaunty Jackalope (I tried a few
> server-dedicated distros, but JJ is what I'm comfortable with).  The
> HOWTOs I've found on the net make building a RAID array using mdadm
> pretty simple, but I keep getting "Device or resource busy" on one or
> more of the RAID drives when I try to do an mdadm build.  What's really
> odd is that the "busy" drive(s) are different each time I reboot the
> machine.  These drives have been fdisk'd to auto-detect RAID partitions,
> are completely empty, and are not mounted -- never *have been* mounted,
> for that matter.  Running an lsof turns up nothing using any of the
> /dev/sd* drives aside from the boot drive.  'tis a pozzlement.

BIOS boot order and other things can affect assignments which is why
they use UUIDs now.  Check the UUIDs using blkid to see if you somehow
ended up with a duplicate (like cloning an existing RAID member
instead of creating each drive separately with fdisk/cfdisk/parted and
mdadm).

>        The other problem is that when I experimentally tried creating a RAID
> array out of the drives that *weren't* busy, some odd things happened.
> The array built successfully, as far as I could tell -- no error
> messages, and it showed up as an active /dev/md0 in /proc/mdstat, but
> when I rebooted the computer, mdadm won't show /dev/md0 as an active
> array device, although it'll accept start/stop commands.  Trying to
> build the array again from scratch yields a bunch of "device appears to
> already be part of a RAID array" error messages.  Thing is, I can't seem
> to get rid of the old array so I can start over again.

Stop the arrays and try zeroing the drives using dd.

Also check mdadm bug reports:
https://bugs.launchpad.net/ubuntu/+source/mdadm?field.searchtext=&orderby=-datecreated