Hi,
this is normal & expected. You have a single disk in your system, which is already used as the boot disk by Proxmox VE.
As for the partitions, expected as well - the first too are boot partitions and the third is the actual root partition of the system.
As to why it says that the root partition (so
/dev/nvme0n1p3
) is not mounted - that is simply due to how LVM storage works underneath.
If you want to actually add
another storage (so e.g. a directory storage), you need a free (thus second) disk in the system.
As you seem to have choosen either ext4 or XFS during installation, you have a
local
and
local-lvm
storage defined for your guests.
I'd suggest reading a bit into the
Storage chapter of our admin guide, hopefully that should clear things up a bit regarding storage in Proxmox VE.