Re: RAID5 - Disk failed during re-shape

[NeilBrown <neilb@suse.de>]

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On Sat, 11 Aug 2012 10:42:01 +0200 Sam Clark <sclark_77@hotmail.com> wrote:

> Thanks for the response Phil. 
> 
> I was thinking that 'toast' was the case, and have been looking into my backups (not so great, though the critical data is fine). 
> 

If you've got backups, then that is likely the most reliable solution - sorry.



> I think you are toast, as I saw nothing in the metadata that would give
> you a precise reshape restart position, even if you got Neil to work up
> a custom mdadm that could use it.  The 11.4% could be converted into an
> approximate restart position, perhaps.
> 
> Neil, is there any way to do some combination of "create
> --assume-clean", start a reshape held at zero, then skip 11.4% ?

The metadata might contain the precise reshape position - but "mdadm
--examine" won't be displaying it.
If you can grab the last 128K of the device (probably using 'dd' with
'skip=xxx' I would be able to check and see.

If you can tell me:
  exactly how big the devices are (sectors)
  what the chunk size of the array was (probably 64K)

and get me that last 128K of a few devices, then I can provide you a shell
script that will poke around in sysfs and activate the array in read-only
mode which might allow you to mount it and copy out any important data.
After that you would need to re-create the array.

I don't think it is really practical to get the array fully working again
with recreating from scratch once you have all the important data.

NeilBrown


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