Re: Recover data from accidentally created raid5 over raid1

["John Stoffel" <john@stoffel.org>]

>>>>> "Moritz" == Moritz Rosin <moritz.rosin@itrosinen.de> writes:

> Hey there,
> unfortunately I have to admit, that I learned my lesson the hard way 
> dealing with software raids.

> I had a raid1 running reliable over month using two 4TB HDDs.
> Since I ran short on free space I tried to convert the raid1 to a raid5 
> in-place (with the plan to add the 3rd HDD after converting).
> That's where my incredibly stupid mistake kicked in.

> I followed an internet tutorial that told me to do:
> mdadm --create /dev/md0 --level=5 --raid-devices=2 /dev/sdX1 /dev/sdY1

Please share the link to the tutorial so we can maybe shame that
person into fixing it.  Or removing it.  

> I learned that I re-created a raid5 array instead of converting the 
> raid1 :-(

Yeah, I think you're out of luck here.  What kind of filesystem did
you have on your setup?  Were you using MD -> LVM -> filesystem stack?
Or just a raw filesystem on top of the /dev/md?  device?

> Is there any chance to un-do the conversion or restore the data?
> Has the process of creation really overwritten data or is there
> anythins left on the disk itself that can be rescued?

If you have any information on your setup before you did this, then
you might be ok, but honestly, I think you're toast.

John