Any kind of partition can be mounted on any directory on the filesystem. As an example, if you have “/dev/sdb1” (adjust for your device), then you can mount it on “/usr/local” and then all content there goes through sdb1. If you umount sdb1, then the original content shows up again. You can selectively copy what is already on “/usr/local” so that the old content does not appear to go away upon mount. Most cuda content is there. For details, see:
https://forums.developer.nvidia.com/t/how-to-install-linux-on-system-disk-and-cuda-on-ssd/188834/2