[Feature Request] Keep Volume Data already in Mount Folder + copy --refresh for volumes

I have “old” containers on the DIR backend that have MySQL on them. I copied one DIR container over to another server, with ZFS, with a container that has a custom volume at path=/var/lib/mysql (to have recordsize=16k on the zfs filesystem, thanks for showing me that @stgraber!).

The problem is that zfs list does not show any storage usage of the mysql-volume as the config of the original conatiner was copied over as well of course.

What is the best way to achieve the mysql data being on the volume as attaching the volume again will empty the mysql folder? And importing a mysqldump won’t work as the mysql server won’t start with an empty folder. And backing up the folder and putting it back does not work either.

It would be nice to have a built in way to handle this kind of situation for volumes.
Is there?

Attach the directory to an alternate path in the container, move the data over to it, then change the config to attach it to the expected location.

So moving the folder content out and back again after volume attachment gave me data corruption. The container would start up and run for a minute and mysql would crash, the error hinted towards data corruption according to a StackOverflow answer.
Had to use a different way and migrate the application on application level.

After doing that I am trying to move the volumes to the first server again.
I noticed that you can’t overwrite volumes as you could containers with --refresh.
I would like to request that freature please.

Additionally I would like to request a feature where you could savely move data that was in the mouting location of a volume back into it. Maybe with --keep-data.
Thanks for considering!