[linux-lvm] inconsistency between thin pool metadata mapped_blocks and lvs output

[John Hamilton]

I saw something today that I don't understand and I'm hoping somebody can
help.  We had a ~2.5TB thin pool that was showing 69% data utilization in
lvs:

# lvs -a
  LV                    VG       Attr       LSize  Pool Origin Data%
Meta%  Move Log Cpy%Sync Convert
  my-pool         myvg twi-aotz--  2.44t             69.04  4.90
  [my-pool_tdata] myvg Twi-ao----  2.44t
  [my-pool_tmeta] myvg ewi-ao---- 15.81g

However, when I dump the thin pool metadata and look at the mapped_blocks
for the 2 devices in the pool, I can only account for about 950GB.  Here is
the superblock and device entries from the metadata xml.  There are no
other devices listed in the metadata:

<superblock uuid="" time="34" transaction="68" flags="0" version="2"
data_block_size="128" nr_data_blocks="0">
  <device dev_id="1" mapped_blocks="258767" transaction="0"
creation_time="0" snap_time="14">
  <device dev_id="8" mapped_blocks="15616093" transaction="27"
creation_time="15" snap_time="34">

That first device looks like it has about 16GB allocated to it and the
second device about 950GB.  So, I would expect lvs to show somewhere
between 950G-966G Is something wrong, or am I misunderstanding how to read
the metadata dump?  Where is the other 700 or so GB that lvs is showing
used?

Thanks,

John
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listman.redhat.com/archives/linux-lvm/attachments/20180510/e868ee4f/attachment.htm>