Lion was designed to be installed on a drive that has been partitioned into one volume (or two if Boot Camp is installed), and the target volume should not be part of a RAID.

If you attempt to upgrade from Snow Leopard to Lion, and are booted from a RAID volume or a volume on a uniquely partitioned drive, the Lion installer will give an alert stating “Some features of Mac OS X Lion are not supported for the disk”. You will be able to actually install Lion and boot from it, however FileVault 2 cannot be enabled, and the Lion Recovery HD partition will not be created.