old raid0run

old raid0run

[Marco Scoffier]

Hello all,

I have an old raid0 with no superblocks.

I have just upgraded the machine with this raid and mdadm is incapable of
mounting it.  Unfortunately raidtools will no longer compile*.  So I am a
bit stuck as I would like to save the data on this raid0.

Can I create a new raid0 using mdadm ?

  mdadm -C -n 2 -c 128 -l 0 /dev/md0 /dev/hde1 /dev/hdg1

or should I build a new raid0 and then upgrade that to a raid0 with
superblocks (how would I do that?)

Thanks for any pointers,



As there are no super-blocks mdadm is
giving very little information:

mdadm -E /dev/hde1
mdadm: No md superblock detected on /dev/hde1.
mdadm -E /dev/hdg1
mdadm: No md superblock detected on /dev/hdg1.

mdadm -As /dev/md0 
mdadm: /dev/hde1 has no superblock - assembly aborted


the raidtab is clear:

# Sample raid-0 configuration

raiddev                 /dev/md0

raid-level              0    # it's not obvious but this *must* be 
                             # right after raiddev

persistent-superblock   0    # set this to 1 if you want autostart,
                             # BUT SETTING TO 1 WILL DESTROY PREVIOUS
                             # CONTENTS if this is a RAID0 array created
                             # by older raidtools (0.40-0.51) or mdtools!

chunk-size              128

nr-raid-disks           2
nr-spare-disks          0

device                  /dev/hde1
raid-disk               0

device                  /dev/hdg1
raid-disk               1

-- 
Marco

* the raidtools compile error is some awfull stuff in a macro.  There is a
bug report here: http://bugs.gentoo.org/show_bug.cgi?id=165917

Re: old raid0run

[Michael Tokarev]

Marco Scoffier wrote:
> Hello all,
> 
> I have an old raid0 with no superblocks.
> 
> I have just upgraded the machine with this raid and mdadm is incapable of
> mounting it.  Unfortunately raidtools will no longer compile*.  So I am a
> bit stuck as I would like to save the data on this raid0.
> 
> Can I create a new raid0 using mdadm ?
> 
>   mdadm -C -n 2 -c 128 -l 0 /dev/md0 /dev/hde1 /dev/hdg1

Well, mdadm is able to assemble it.  It's called 'build' (--build) --

  mdadm --build -n 2 -c 128 -l 0 /dev/md0 /dev/hde1 /dev/hdg1

> or should I build a new raid0 and then upgrade that to a raid0 with
> superblocks (how would I do that?)

I think the best option is to convert it to raid0-with-superblocks.
For that, I'd go this route:

  - build the array as above
  - fsck the filesystem on it
  - resize the filesystem to be, say, 1Mb smaller
  - stop the array
  - create new array as you've shown above with -C
  - and finally resize the filesystem to utilize all available space

Or something like that, anyway.

Sure, backing up data and restoring it after creating the array is
safer.

> Thanks for any pointers,
> 
> As there are no super-blocks mdadm is
> giving very little information:
> 
> mdadm -E /dev/hde1
> mdadm: No md superblock detected on /dev/hde1.

Well, it's expectable.  -E = show superblock contents.

> mdadm -As /dev/md0 
> mdadm: /dev/hde1 has no superblock - assembly aborted

Assembly needs devices with superblocks.  Try -B.

/mjt

Re: old raid0run

[Marco Scoffier]

On Sun, 11 Feb 2007 09:59:29 +0300, Michael Tokarev wrote:

> Marco Scoffier wrote:
>> Hello all,
>> 
>> I have an old raid0 with no superblocks.
>> 

> Well, mdadm is able to assemble it.  It's called 'build' (--build) --
> 
>   mdadm --build -n 2 -c 128 -l 0 /dev/md0 /dev/hde1 /dev/hdg1
>

Thanks for the clarification Micheal.  Reading the docs, I got a little
confused about what --build was for.

>> or should I build a new raid0 and then upgrade that to a raid0 with
>> superblocks (how would I do that?)
> 
> I think the best option is to convert it to raid0-with-superblocks. For
> that, I'd go this route:
> 
>   - build the array as above
>   - fsck the filesystem on it
>   - resize the filesystem to be, say, 1Mb smaller - stop the array -
>   create new array as you've shown above with -C - and finally resize
>   the filesystem to utilize all available space
> 

Thanks for these steps.  I am running them now.

Thanks for an amazingly fast and clear response.

-- 
Marco