When creating logical volumes, you may want to backup your data before you run 'pvcreate'. Take it from me, who is sitting at his computer at 1 in the morning pulling his hair out, as he lost a *lot* of data, and is currently reinstalling Ubuntu 7.10. Yeah, I know all about version control and keeping backups. I don't want to hear it. Just FYI- backup your data *before* running 'pvcreate'.
That is all.