LVM - pvmove to a smaller volume
my understanding is that if you add additional PV (physical volume) to a VG (volume group) that hosts your LV (logical volume) you should be able to issue pvmove like so:
# Move a range of physical extents to a
# specific PV (which must have suffi‐
# cient free extents).
pvmove /dev/sdb1:1000-1999 /dev/sdc1
taken from man pvmove