Run the below commands to create LVM for 2 disks:

pvcreate /dev/sda1 /dev/sda2
vgcreate [Vol-name] /dev/sda1 /dev/sda2
lvcreate [Vol-name] -L +11G -n [Lv-name]

Here, [Vol-name] means the Volume group name and [Lv-name] refers to the logical volume name. -n is for specifying the name and -L is for total amount of LVM to be occupied.