LVM ?

Hi all, I'm planning on replacing our WinXP server (it's just a file server) with SuSE 9.1. I plan on putting 3, 40MB drives in it and using LVM to span the disks. Since I'm not too familar with LVM, I'm interested in others experiences. Should I use LVM to span all three disks or should I put the OS on the first one and use LVM to span 2 and 3? Any tips or anything I should watch out for? Thanks- Dan