Umm, no. You create a logical volume(s) from volume group(s) of the size(s) you want. These aren't "partitions", but they sort of act like them.
Any single logical volume cannot be created from multiple volume groups. A single volume group, however, can have multiple logical volumes.
You can create multiple volume groups from the available physical volumes -- in whole physical volume sizes (that is, a physical volume can only be in one volume group at a time).
If I've missed something I'm sure someone will point it out.
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