http://man7.org/linux/man-pages/man7/lvmthin.7.html
Command to repair a thin pool:
lvconvert --repair VG/ThinPoolLV
Repair performs the following steps:
1. Creates a new, repaired copy of the metadata.
lvconvert runs the thin_repair command to read damaged metadata from
the existing pool metadata LV, and writes a new repaired copy to the
VG's pmspare LV.
2. Replaces the thin pool metadata LV.
If step 1 is successful, the thin pool metadata LV is replaced with
the pmspare LV containing the corrected metadata. The previous thin
pool metadata LV, containing the damaged metadata, becomes visible
with the new name ThinPoolLV_tmetaN (where N is 0,1,...).
If the repair works, the thin pool LV and its thin LVs can be
activated, and the LV containing the damaged thin pool metadata can
be removed. It may be useful to move the new metadata LV (previously
pmspare) to a better PV.
If the repair does not work, the thin pool LV and its thin LVs are
lost.
This info seems to conflict with Red Hat advice. Red Hat says if metadat volume is full
don't run a lvconvert --repair operation. Now I am confused. I am familiar with LVM
and comfortable with it but this is my first time trying to repair thin LVM. The concepts
of a metadata volume are new to me.