[linux-lvm] Problem with partially activate logical volume

[Roger James]

The procedure outlined should at least get you back to a state where the lv 
is consistent but with blank sectors where the data is missing. I would 
suggest using dd to make a backup partition image. Then you can either work 
on that or the original to mend the fs.

On 27 July 2022 11:50:07 Roger Heflin <rogerheflin at gmail.com> wrote:

> I don't believe that is going to work.
>
> His issue is that the filesystem is refusing to work because of the
> missing data.
>
> man debugfs
>
> It will let you manually look at the metadata and structures of the
> ext2/3/4 fs.  You will likely need to use the "-c" option.
>
> It will be very manual and you should probably read up on the fs
> structure a bit.
>
> A data recovery company could get most of the data back, but they
> charge 5k-10k per TB, so likely close to 100k US$.
>
> And the issues will be that 1/3 of the metadata was on the missing
> disk, and some of the data was on the missing disk.
>
> I was able to do debugfs /dev/sda2  (my /boot) and do an ls and list
> out the files and then do a dump <filename> /tmp/junk.out and copy out
> that file.
>
> So the issue will be writing up a script to do lses and find all of
> the files and dump all of the files to someplace else.
>
> On Wed, Jul 27, 2022 at 2:39 AM Roger James <roger at beardandsandals.co.uk> 
> wrote:
>>
>> Try https://www.linuxsysadmins.com/recover-a-deleted-physical-volume/?amp
>>
>> On 26 July 2022 09:16:32 Ken Bass <daytooner at gmail.com> wrote:
>>>
>>> (fwiw: I am new to this list, so please bear with me.)
>>>
>>> Background: I have a very large (20TB) logical volume consisting of 3 
>>> drives. One of those drives unexpectedloy died (isn't that always the case 
>>> :-)). The drive that failed happened to be the last PV. So I am assuming 
>>> that there is still 2/3 of the data still intact and, to some extent, 
>>> recoverable. Although, apparently the ext4 fs is not recognised.
>>>
>>> I activated the LV partially (via -P). But running any utility on that (eg: 
>>> dumpe2fs, e2fsck, ...) I get many of these  in dmesg:
>>>
>>> "Buffer I/O error on dev dm-0, logical block xxxxxxx, async page read."  
>>> The thing is, the xxxxxxx block is on the missing drive/pv.
>>>
>>> I have also tried some recovery software, but eventually get these same 
>>> messages, and the data recovered is not really useful.
>>>
>>> Please help! How can I get passed that dmesg error, and move on. 14TB 
>>> recovered is better than 0.
>>>
>>> TIA
>>> ken
>>>
>>>
>>> _______________________________________________
>>> linux-lvm mailing list
>>> linux-lvm at redhat.com
>>> https://listman.redhat.com/mailman/listinfo/linux-lvm
>>> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>>>
>>
>> _______________________________________________
>> linux-lvm mailing list
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>> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>
> _______________________________________________
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