# dd if=/dev/zero of=~/tmp.img bs=10M count=50
# losetup /dev/loop0 ~/tmp.img
# pvcreate /dev/loop0
  Physical volume "/dev/loop0" successfully created
# vgcreate vg1 /dev/loop0
  Volume group "vg1" successfully created
# lvcreate -T -L200m vg1/pool
  Logical volume "lvol0" created
  Logical volume "pool" created
# lvcreate -T -V1g --name data0 vg1/pool
  Logical volume "data0" created
# lvs
  LV      VG   Attr       LSize   Pool Origin Data%  Move Log Cpy%Sync Convert
  data0   vg1  Vwi-a-tz--   1,00g pool          0,00
  pool    vg1  twi-a-tz-- 200,00m               0,00
# mkfs.ext2 /dev/vg1/data0
...
# mkdir /mnt/{data,snap}
# mount /dev/vg1/data0 /mnt/data/
# touch /mnt/data/A
# lvcreate --name data1 -s vg1/data0
  Logical volume "data1" created
# lvs
  LV      VG   Attr       LSize   Pool Origin Data%  Move Log Cpy%Sync Convert
  lv_home Vg0  -wi-ao---- 200,00g
  lv_root Vg0  -wi-ao----  40,00g
  data0   vg1  Vwi-aotz--   1,00g pool          1,67
  data1   vg1  Vwi---tz-k   1,00g pool data0
  pool    vg1  twi-a-tz-- 200,00m               8,56
# lvchange -ay vg1/data1
# lvs
  LV      VG   Attr       LSize   Pool Origin Data%  Move Log Cpy%Sync Convert
  data0   vg1  Vwi-aotz--   1,00g pool          1,67
  data1   vg1  Vwi---tz-k   1,00g pool data0
  pool    vg1  twi-a-tz-- 200,00m               8,56