I’ve found these useful examples about LVM, Article By Roger Hosto
Let’s start with what LVM is; in short it’s away to manage disk volumes in more of a user friendly way, whether they are whole hard disk, disk partitions, or SAN disk. Logical Volume Manager gives the Administrator much more flexibility in allocating, re-sizing, and moving storage around. With that being said, the greatest advantage is having the ability to add additional disk space with relative ease, which with Moore’s Law and Kryder’s Law  floating around makes life a little easier on your System Administrator.
Now that you are all interested in using LVM, let’s bust out a new hard-drive or re-partition our hard-disk and have at it. Woo! Hang on a minute! That sounds like a pain just to play around with something. That’s what I thought too, so here is a way to use your existing partitions using loop devices and empty disk images to play around with and get use to the commands.
I have personally tested this on RHEL 4 and 5, but I don’t see why this couldn’t be done on any current version of Linux.