Each LVM logical volume is represented by a dm-* file under /dev.
Sometimes it is difficult to see which dm is associated to which lv.
Fortunately the magic of shell can help out. Below you have a couple of examples.

core:~# lvdisplay|awk  '/LV Name/{n=$3} /Block device/{d=$3; sub(".*:","dm-",d); print d,n;}'
dm-1 /dev/datavg/mylv
dm-2 /dev/datavg/weblv
dm-4 /dev/datavg/ftplv
dm-5 /dev/datavg/blahlv
dm-7 /dev/datavg/backups
dm-8 /dev/rootvg/homelv
dm-0 /dev/rootvg/slashlv
dm-9 /dev/rootvg/tmplv
dm-10 /dev/rootvg/usrlv
dm-11 /dev/rootvg/varlv
dm-12 /dev/rootvg/srclv
dm-14 /dev/rootvg/swap0
dm-15 /dev/rootvg/fileslv

16:16:16 root@eeny:~# ls -la /dev/disk/by-id/ | grep -i dm-name
lrwxrwxrwx 1 root root   10 Nov 18 21:59 dm-name-dataBvg-dataB -> ../../dm-5
lrwxrwxrwx 1 root root   10 Nov 18 21:59 dm-name-dataCvg-dataC -> ../../dm-3
lrwxrwxrwx 1 root root   10 Nov 18 21:59 dm-name-mediaBvg-mediaB -> ../../dm-4
lrwxrwxrwx 1 root root   10 Jan 28 14:40 dm-name-mediaCvg-mediaC -> ../../dm-2
lrwxrwxrwx 1 root root   10 Nov 18 21:59 dm-name-rootvg-home -> ../../dm-8
lrwxrwxrwx 1 root root   10 Nov 18 21:59 dm-name-rootvg-root -> ../../dm-0
lrwxrwxrwx 1 root root   10 Nov 18 21:59 dm-name-rootvg-swap_1 -> ../../dm-1
lrwxrwxrwx 1 root root   10 Nov 18 21:59 dm-name-rootvg-tmp -> ../../dm-7
lrwxrwxrwx 1 root root   10 Nov 18 21:59 dm-name-rootvg-var -> ../../dm-6