[linux-lvm] Problem with partially activate logical volume

[Roger Heflin]

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
>>
>>
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>>
>
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