For some use cases I'd like to have the possibility to create a volume with
docker volume create, and fill it with data. Then I want to create a new volume that is only a copy of the first one, but no data needs to be copied, only changed files should be written.
This is what Docker already does with images and containers using aufs or overlayfs. Do you know any strategy to solve this for volumes? If it does not work with docker volumes right now, can you tell me how to do something like this on the Docker host? (Then I could mount those folders from the host.)
By now I have two use cases for it, maybe you have a completely different idea to solve it:
Very big Git repository (around 10GB): I need to run multiple containers with this repository, some of them also commit changes. So it must be independent from other containers, push commits to the remote repository and then the copied volume may be deleted.
Very big mysql databases (around 130GB): For testing purposes and other migration tasks I'd like to not have to copy the whole database.