Proxmox Expand /dev/pve/data

Hi all,

I recently upgraded the drives in my Proxmox machine to 1TB from 300GB. Is there an easy way to extend the /dev/pve/data partition so I can use all this extra space?

I've tried this already:

root@proxmox:~# lvextend -L800G /dev/mapper/pve-data
Extending logical volume data to 800.00 GiB
Insufficient free space: 163360 extents needed, but only 4095 available

root@proxmox:~# lvextend -L800G /dev/pve/data
Extending logical volume data to 800.00 GiB
Insufficient free space: 163360 extents needed, but only 4095 available