Re: change from raid 5 to raid 6 interrupted

[NeilBrown <neilb@suse.de>]

On Fri, 22 Apr 2011 16:23:19 +0100 John Robinson
<john.robinson@anonymous.org.uk> wrote:

> (Please always remember to cc the list when replying; cc readded)
> 
> On 22/04/2011 16:09, Raphael Müller wrote:
> > Ok i forgot to say, that the backup file is also gone... (my mistake)
> >
> > is this backup file the only option i got?
> 
> Without the backup file you've almost certainly lost some data. I 
> suspect there is a way of restarting the array and reshape without the 
> backup file, but I don't know what it is - you'll have to wait for a 
> proper guru to get back to you with an answer.
> 

With mdadm 3.2.1 there is a new flag "--invalid-backup".  It tells mdadm that
you know that the backup file is invalid, but you want it to continue anyway
(and risk having some corrupted data).

You still need to give a backup file, but it can be a newly created empty
file.

So:
  # install mdadm 3.2.1
  > /root/my-backup
  mdadm -A /dev/mdthing --backup-file=/root/my-backup  \
  --invalid-backup /dev/device1 /dev/device2 ....

should get you going again.

NeilBrown
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