Start with one drive. Create a spanned volume, volume group, and logical volume.
pvcreate /dev/sdb vgcreate STORAGE1 /dev/sdb lvcreate -l +100%FREE STORAGE1 -n storage1
Add an additional disk (you could have done this in one step, but I want to illustrate adding a disk).
pvcreate /dev/sdc vgextend STORAGE1 /dev/sdc lvextend -l +100%FREE /dev/STORAGE1/storage1
You can view the status of the physical and logical volumes.
pvdisplay vgdisplay lvdisplay
Feel free to contact me with questions or feedback regarding this article.