... lun 2 { path /volX/diskimages/diskname.img size 500G } ...
touch /volX/diskimages/diskname.img
service ctld restart
iscsiadm -m node -R
vgdisplay | grep "VG Name"
vgextend {VG Name} {Phyical Disk}
It might be tempting to extend the logical volume from the shell, but with Proxmox is much eaiser to work with if that is done from the Web GUI.