Quick note on Portainer and Asustor NAS
If you're running Docker Stacks or containers instead of using the Asustor's App Central to install their versions of software:
By default, the stacks use ephemeral storage. If you want to store your stack's files on persistent storage on your main storage volume, map the storage to:
/volume1/Docker/
You could probably use something other than Docker, but the Docker daemon definitely has access to this directory.