Data recovery -- thin provisioned LVM metadata (?) problem after hardware failure

[Zdenek Kabelac <zdenek.kabelac@gmail.com>]

Dne 25. 04. 23 v 15:49 haaber napsal(a):
> Dear all,
> 
> I had a lethally bad hardware failure and to replace the machine.? Now I try 
> to get some data back that is not contained in half-year backups ... (I know! 
> but it's too late to be sorry). OK,? the old SSD is attached? via usb adapter 
> to a brand new machine. I started
> 
> sudo pvscan
> sudo vgscan --mknodes
> sudo vgchange -ay
> 
> Here is the? unexpected output:
> 
>  ?PV /dev/mapper/OLDSSD ? VG?? vg0 ????? lvm2 [238.27 GiB / <15.79 GiB free]
>  ? Total: 1 [238.27 GiB] / in use: 1 [238.27 GiB] / in no VG: 0 [0?? ]
>  ? Found volume group "vg0" using metadata type lvm2
>  ? Check of pool vg0/pool00 failed (status:1). Manual repair required!
>  ? 1 logical volume(s) in volume group "vg0" now active
> 
> then I consulted dr. google for diagnosis, but found only little help. This one
> 
> https://mellowhost.com/billing/index.php?rp=/knowledgebase/65/How-to-Repair-a-lvm-thin-pool.html
> 
> suggested to deactivate all sub-volumes so that a repair can work correctly. 
> It happened that only swap was
> active, so I deactivated it. But repair does still not work:
> 
> lvconvert --repair vg0/pool00
> terminate called after throwing an instance of 'std::runtime_error'
>  ? what():? transaction_manager::new_block() couldn't allocate new block
>  ? Child 21255 exited abnormally
>  ? Repair of thin metadata volume of thin pool vg0/pool00 failed
> (status:-1). Manual repair required!
> 
> 
> I would like to find a good soul out there that can give more hints. In 
> particular,
> could it be a metadata overflow? How to check? I seek not for repair, but a 
> "once only"
> read access to the pool data ....
> 

Hi

Check  'man lvmthin'  "Metadata check and repair" section.
If the 'repair' does not work make sure you have 'latest' thin_repair tool (>= 
v0.9) - as older distros come with ancient less capable version of this tool.

Since you likely already tried to repair metadata - you may need to do the 
manual repair with the use  of  _meta0  LV  (see man lvmthin).

If you cannot get  'workable' metadata with  0.9 of thin_repair tool - you 
will likely need to create a BZ - upload compressed content of your metadata 
device for futher analysis - whether it's somehow possible to recover bTree.


Regards

Zdenek