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

[David McMillan]

David McMillan wrote:
> Jeff Hanson wrote:
>> 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).
> 
> 	Hm.  Okay, I'll try that.

	Busy, busy, busy.  But I finally got time to sit down and do all of 
this.  So, I did:
	dd if=zero of=/dev/sdx for all five of the drives I want to RAID.
	Confirmed that each disk no longer had a partition table using fdisk.
	Used fdisk to partition each drive as Linux Raid Autodetect.
	Ran the following command:  sudo mdadm --create --verbose /dev/md0 
--level=10 --raid-devices=4 /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1 
--spare-devices=1 /dev/sdf1
	And what I got was:
mdadm: layout defaults to n1
mdadm: chunk size defaults to 64K
mdadm: Cannot open /dev/sde1: Device or resource busy
mdadm: /dev/sdf1 appears to be part of a raid array:
     level=raid10 devices=4 ctime=Sat Oct 10 02:50:35 2009
mdadm: create aborted

	Running blkid gave me this:
  sudo blkid
/dev/sda5: UUID="cc3d2e49-6504-459d-af40-eeb214cc41cb" TYPE="ext3"
/dev/sda6: UUID="9bf141dd-1ef9-4bf6-b55e-b699229fcb08" TYPE="ext3"
/dev/sda7: TYPE="swap" UUID="a246c936-2a1f-4d57-a4ac-c0fa72baa766"
/dev/sde1: UUID="fdd19ba2-6598-f2fa-2621-c6fd51a58e1d" TYPE="mdraid"
/dev/sdf1: UUID="02138639-c13a-b909-2621-c6fd51a58e1d" TYPE="mdraid"

	So... I'm lost.  I did all of this in one sitting -- nothing should 
have mounted or taken up /dev/sde or /dev/sdf in between the time I 
fdisk'd them and the time I ran mdadm.  Heck, it was less than five 
minutes between commands.  I can't figure out what's going on here, or 
how to break loose sde and sdf from whatever's got them.

	Just for giggles, I did a 'sudo rm -r /dev/md*', and that got rid of 
the /dev/sde error, but the /dev/sdf error lingers.

	Any thoughts on what I should try next?


>>>        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.
> 
> 	Ah, dd.  Is there anything it *can't* do?
> 	Actually, I've already done this (do you know how *long* it takes to 
> dd-zero five full 1TB drives?  Yowza!), and found that sometimes even 
> "sudo dd" will generate the "busy" error.  I'm working around it for the 
> moment.  I should have fully zer0'd drives to try again with when I get 
> home from work tonight.
> 
>> Also check mdadm bug reports:
>> https://bugs.launchpad.net/ubuntu/+source/mdadm?field.searchtext=&orderby=-datecreated
> 
> 	D'oh.  Why didn't I think of that?
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