[linux-lvm] Repair thin pool

M.H. Tsai mingnus at gmail.com
Mon Feb 8 18:03:39 UTC 2016

2016-02-08 16:56 GMT+08:00 Joe Thornber <thornber at redhat.com>:
> On Fri, Feb 05, 2016 at 07:44:46PM +0800, M.H. Tsai wrote:
>> I also wrote some extension to thin-provisioning-tools (not yet
>> published. the code still need some refinement...), maybe it could
>> help.
> I'd definitely like to see what you changed please.
> - Joe

I wrote some tools to do "semi-auto" repair, called thin_ll_dump and
thin_ll_restore (low-level dump & restore), that can find orphan nodes
and reconstruct the metadata using orphan nodes. It could cope the cases
that the top-level data mapping tree or some higher-level nodes were
broken, to complement the repairing feature of thin_repair.

Although that users are required to have knowledge about dm-thin metadata
before using these tools (you need to specify which orphan node to use), I
think that these tools are useful for system administrators. Most thin-pool
corruption cases I experienced (caused by power lost, broken disks, RAID
corruption, etc.) cannot be handled by the current thin-provisioning-tools
--  thin_repair is fully automatic, but it just skips broken nodes.
However, those missing mappings could be found in orphan nodes.

Also, I wrote another tool called thin_scan, to show the entire metadata
layout and scan broken nodes. (which is an enhanced version of
thin_show_block in branch low_level_examine_metadata -- I didn't notice
that before... maybe the name thin_show_block sounds more clear?)

What do you think about these features? Are they worth to be merged to the

Ming-Hung Tsai
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