Ok. Thanks Michael and Vincent. To confirm, docker is storing the images in the Moby instance, so its all in the virtual disk. Which means, that if I need to relocate the storage to another physical drive (outside of hyper-v), I have to move that file - and of course change the VM info, or make that folder a symbolic link (or similar) to somewhere else.
Thank you. I was worried about maxing out my C drive, which is not very large.
David