seafile consists of the DB and the seafile-folder. with this two you can always migrate.
If you can keep the old mounting point name and point it to the new device it should be a no-brainer.
but you should shut down the seafile-services, then copy the data-folder and recreate the mountpoint on the lvm, then start the services again…
even if you cannot keep the mounting point to the data-folder it should be no problem.
You can run the setup again and it should see existing DB and data-folder.
One user also stated executing the minor-update.sh instead of running setup again did well for him.
maybe minor-update.sh is less “harmfull”
here is the link to that topic:
anyway make sure you only delete your old data when seafile is using the new folder and you have done testing !
btw: you can have a look at zfs instead of lvm.
I use it now for a while as a raid 1 for the seafile-data folder