LVM

So I am working on adding a 320GB drive to my MythTV box. I already know how to add the drive and create the mountpoint for it. What I really want to do though is make the computer not know the difference between the two drives. If it runs out of space on one it will just start using the next. I have figured out to do this I will have to use LVM(logical volume management (I think)) to do this. I will post directions once I figure this out. I am getting close but havent had time to follow up on some of the research I did recently.

Thanks and God Bless
Aaron