Proxmox uses BTRFS subvolumes for block level type volumes : https://pve.proxmox.com/wiki/BTRFS
As said, if homelab/budget constraint , use M2 disc N1 as LVMthin , then backup (like an asynchronous raid) to the M2 disc N2 , with PBS.
If N1 fails, replace it, restore from N2.
For business, it's...