1. Use multiple volume groups to define classes of storage.
2. Use full disk physical volumes over partitions.
3. I like unique naming of volume groups just so that if
a drive lands else where, and it presents itself to the system,
it will not collide with existing volume group names.
(but there is good reason for not doing this... and really
only a factor if you have a tendency to throw drives into
different computers all of the time)