On Wed, 14 Dec 2011 14:41:52 -0700 Troy Telford [off-list ref]
wrote:

On 2011-12-14 19:01:01 +0000, Phil Turmel said:

quoted

Hi Troy,

On 12/13/2011 05:42 PM, Troy Telford wrote:

Let me guess:  You have version 0.90 superblock, and sdl1 covers the 
whole device?

sdl1 does cover the entire device, but I'm fairly certain I do not have 
a 0.90 superblock (Unless 0.90 was the standard version for Linux 2.6 
about two years ago.)

It is mdadm that determines the superblock rather than the kernel, but you
definitely have 0.90 superblocks - I can tell from the /proc/mdstat output
(it doesn't list a version, so it must be 0.90).

Unfortunately, I'm not sure how to get my current superblock version:
$ sudo mdadm --examine /dev/md2
mdadm: No md superblock detected on /dev/md2.

I find it curious that I can't detect the superblock for the MD device, 
even though the device is up, active, and working.

The array doesn't have a superblock.  Each member device does.
  mdadm --examine /dev/sdl1

quoted

Short term, change your mdadm.conf to only accept device names that end 
with a digit.  Like so:

DEVICE /dev/sd[a-z][1-9]

OK, I'll give that a whirl.  For the record, it was DEVICE partitions 
previously.

quoted

Then rebuild your initramfs to include the new mdadm.conf.

Long term, rebuild your array with v1.x metadata.

You know, I was hoping to be able to wait until btrfs handles RAID-6 
(or "raid-z") arrays by the time I had to rebuild the array.  I guess 
I'm not that lucky.

You don't really need to rebuild the array.  Just change the DEVICE line and
all will be happy.

(but I advise you never to plan on using software that hasn't be released yet
- that way lies madness).

NeilBrown