Unable to mount hammer file system Undo failed

[Wojciech Puchar]

>> UFS use flat on disk structure. inodes are at known places.
>> 
>> I don't know how HAMMER data is placed, but seems everything is dynamic.
>> 
>> any link to description of HAMMER on disk layout?
>
> Please, read hammer(8) (at the subcommand "recover").
thank you very much.

While such recovery is painfully slow (it scans entire image not just 
selected predefined areas like fsck_ffs) it DO EXIST.

Seems i have to make some more tests with intentionally broken hardware, 
which i don't have at the moment.