What I think you’re getting at is to add an existing dataset from an existing pool there, then let PM rep it for you.
Here’s what I’d try. Add that pool as above, control-click both VM and container types in the dialog you get. Now go to your VM and add a new virtual drive, with a size that’s bigger than the dataset you want to add by whatever amount you think you will ever want for it. Stop the VM and on the host, edit the vm configuration file to point that new virtual drive at the storagename:dataset of the existing dataset you want to use. Start the VM and see what you get. Then I would expect that proxmox would be able to manage that dataset as if it were a regular one, assuming all the flags match. You will need to have a target store on your other nodes to match the name on the first node for replication to work.
Personally, I would replicate a new dataset from your old one to play with like this before I was certain it did what you want.
Frankly, the easier way to do all this is to copy the data into a regularly made virtual drive on the guest, but this might work fine, too.
So if you go to /etc/pve/nodes/<nodename>/qemu-server on the PM host, you’ll find the config files for any VMs you made, which you can edit offline. In these files you’ll find all the devices etc you define in the GUI. If you fix the line for the new virtual drive to reflect the storagename:dataset of the existing dataset (from
zfs list
on the host), it should attach that dataset via that drive when you boot the guest.Be sure to set the size to reflect at least the existing size of the data in the dataset so you don’t have issues when you bring that drive into the VM as a virtual drive that it’s not addressing the whole dataset because it thinks it ends sooner than it does. You’ll have to fstab that new virtual drive into your guest OS as usual.
As I said, I would highly suggest testing this by repping your dataset to a test dataset before importing it as above just to make sure it works as expected.
And I kinda thought you would be doing this to your NFS server, so just do that same thing but instead of /etc/pve/nodes/<nodename>/qemu-server you want /etc/pve/nodes/<nodename>/lxc for the CT config files. Once you mount the new virt drive in the CT, fix your NFS paths.