Hello,
Thank you for the report. We are aware of this issue. We have a few ideas we are currently testing that could address this issue.
Some technical background: If you have an LVM volume, and create let’s say 2 snapshots of it, both snapshots will have the original volume as their “origin”. If you know run a linstor snapshot rollback (which internally runs a lvconvert --merge $vg/$snapshot as the error message states), it merges the snapshot into its origin. So far everything is as expected. After this command two things have changed: First, the LVM snapshot is now gone (since it got merged), but LINSTOR simply creates a new snapshot to “fix” this point. The second point is more problematic: The second snapshot we created in the beginning, which was completely untouched by our linstor snapshot rollback and lvconvert --merge commands, also “lost” its origin. The data is still there and fine, but this second snapshot can no longer be “merged” into the already rolled back volume.
As a workaround, instead of using linstor snapshot rollback for LVM-THIN setups, you can manually delete the resources (not the -definition) and linstor snapshot resource restore --fr $rsc --tr $rsc --fs $snapshot the snapshot into the same resource-definition.
This is actually one of our plans we are testing right now. The idea sounds fine on LVM_THIN but unfortunately does not work that easily on ZFS setups since there you cannot just delete the volume while it has snapshots (there is a very strict parent-child dependency between ZVOLs and their snapshots).