The administrator can choose between a couple of general strategies for mapping logical extents onto physical extents:
Linear mapping will assign a range of PE's to an area of an LV in order eg., LE 1 - 99 map to PV1 and LE 100 - 347 map onto PV2.
Striped mapping will interleave the chunks of the logical extents across a number of physical volumes eg.,
1st chunk of LE[1] -> PV1[1],
2nd chunk of LE[1] -> PV2[1],
3rd chunk of LE[1] -> PV3[1],
4th chunk of LE[1] -> PV1[2],
and so on. In certain situations this strategy can improve the performance of the logical volume.
LVs created using striping cannot be extended past the PVs they were originally created on in LVM 1.
In LVM 2, striped LVs can be extended by concatenating another set of devices onto the end of the first set. So you can get into a situation where your LV is a 2 stripe set concatenated with a linear set concatenated with a 4 stripe set. Are you confused yet?