# first we need a physical volume which we use the pvcreate tool to create
# I create mine on /dev/sdb3
pvcreate /dev/sdb3
dev_is_mpath: failed to get device for 8:19
Physical volume "/dev/sdb3" successfully created
# pvdisplay shows the newly created volume
pvdisplay
"/dev/sdb3" is a new physical volume of "1.35 TiB"
--- NEW Physical volume ---
PV N........
lvextend -L +10G /dev/kvmvm/w2k8r2evalstandard
Extending logical volume w2k8r2evalstandard to 20.00 GiB
Logical volume w2k8r2evalstandard successfully resized
The above adds 10GB to the logical volume. Of course you must resize the filesystem using other tools to take advantage of the space.........