Re: RAID 1 to RAID 5 failure

[Roy Sigurd Karlsbakk <roy@karlsbakk.net>]

That's probably a good idea. Hope you get most of it out of there.

And find a way to backup when you're done ;)

Vennlig hilsen

roy
-- 
Roy Sigurd Karlsbakk
(+47) 98013356
http://blogg.karlsbakk.net/
GPG Public key: http://karlsbakk.net/roysigurdkarlsbakk.pubkey.txt
--
Hið góða skaltu í stein höggva, hið illa í snjó rita.

----- Original Message -----
> From: "Jorge Nunes" <jorgebnunes@gmail.com>
> To: "Roy Sigurd Karlsbakk" <roy@karlsbakk.net>
> Cc: "Linux Raid" <linux-raid@vger.kernel.org>
> Sent: Tuesday, 5 April, 2022 12:50:20
> Subject: Re: RAID 1 to RAID 5 failure

> Hi roy.
> 
> Thank you for your time.
> 
> Now, I'm doing a photorec on /dev/sda and /dev/sdd and I get better
> results on (some) of the data recovered if I do it on top of /dev/md0.
> I don't care anymore about recovering the filesystem, I just want to
> maximize the quality of data recovered with photorec.
> 
> Best regards,
> Jorge
> 
> Roy Sigurd Karlsbakk <roy@karlsbakk.net> escreveu no dia terça,
> 5/04/2022 à(s) 10:17:
>>
>> I re-did these tests this morning, since I was unsure if I could have made some
>> mistake last night - I was tired. There results were about the same - complete
>> data loss.
>>
>> As for curiousity, I also tried to skip the expand phase after creating the
>> initial raid5 on top of the raid1. After creating it, I stopped it and
>> recreated the old raid1 with --assume-clean. This worked well - no errors from
>> mount or fsck.
>>
>> So I guess it was the mdadm --grow --raid-devices=4 that was the final nail in
>> the coffin.
>>
>> I just hope you find a way to backup your files next time. I'm quite sure we've
>> all been there - thought we were smart enough or something and the shit hit the
>> fan and no - we weren't.
>>
>> Vennlig hilsen
>>
>> roy
>> --
>> Roy Sigurd Karlsbakk
>> (+47) 98013356
>> http://blogg.karlsbakk.net/
>> GPG Public key: http://karlsbakk.net/roysigurdkarlsbakk.pubkey.txt
>> --
>> Hið góða skaltu í stein höggva, hið illa í snjó rita.
>>
>> ----- Original Message -----
>> > From: "Roy Sigurd Karlsbakk" <roy@karlsbakk.net>
>> > To: "Jorge Nunes" <jorgebnunes@gmail.com>
>> > Cc: "Linux Raid" <linux-raid@vger.kernel.org>
>> > Sent: Tuesday, 5 April, 2022 02:29:03
>> > Subject: Re: RAID 1 to RAID 5 failure
>>
>> >> Didn't do a backup :-(
>> >
>> > First mistake… *Always* keep a backup (or three)
>> >
>> >>
>> >> Unmount everything:
>> >
>> > No need - what you should have done, was just to grow the array by
>> >
>> > Partition the new drives exactly like the old ones
>> > mdadm --add /dev/md0 /dev/sd[cd]1 # note that sd[cd] means sdc and sdd, but can
>> > be written this way on the commandline
>> > mdadm --grow --level=5 --raid-devices=4
>> >
>> > This would have grown and converted the array to raid5 without any data loss.
>> >
>> >> $ sudo mdadm --create /dev/md0 -a yes -l 5 -n 2 /dev/sda /dev/sdd
>> >
>> > As earlier mentioned, this is to create a new array, not a conversion.
>> >
>> >> So, my question is: Is there a chance to redo the array correctly
>> >> without losing the information inside? Is it possible to recover the
>> >> 'lost' partition that existed on RAID 1 to be able to do a convenient
>> >> backup? Or the only chance is to have a correct disk alignment inside
>> >> the array to be able to use photorec to recover the files correctly?
>> >
>> > As mentioned, it doesn't look promising, but there are a few things that can be
>> > tried.
>> >
>> > Your data may still reside on the sda1 and sdd1, but since it was converted to
>> > RAID-5, the data would have been distributed among the two drives and not being
>> > the same on both. Further growing the raid, would move the data around to the
>> > other disks. I did a small test here on some vdisks to see if this could be
>> > reversed somehow and see if I could find the original filesystem. I could - but
>> > it was terribly corrupted, so not a single file remained.
>> >
>> > If this was valuable data, there might be a way to rescue them, but I fear a lot
>> > is overwritten already. Others in here (or other places) may know more about
>> > how to fix this, though. If you find out how, please tell. It'd be interesting
>> > to learn :)
>> >
>> > PS: I have my personal notebook for technical stuff at
>> > https://wiki.karlsbakk.net/index.php/Roy's_notes in case you might find that
>> > interesting. There's quite a bit about storage there. Simply growing a raid is
>> > apparently forgotten, since I thought that was too simple. I'll add it.
>> >
>> > So hope you didn't lose too much valuable data
>> >
>> > Vennlig hilsen / Best regards
>> >
>> > roy
>> > --
>> > Roy Sigurd Karlsbakk
>> > (+47) 98013356
>> > --
>> > I all pedagogikk er det essensielt at pensum presenteres intelligibelt. Det er
>> > et elementært imperativ for alle pedagoger å unngå eksessiv anvendelse av
>> > idiomer med xenotyp etymologi. I de fleste tilfeller eksisterer adekvate og
> > > relevante synonymer på norsk.