Re: RAID-6 disk superblock issue

[NeilBrown <neilb@suse.de>]

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On Wed, 14 Dec 2011 14:41:52 -0700 Troy Telford <ttelford.groups@gmail.com>
wrote:

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

> 
> > 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.
> 
> > 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


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