lvm snapshot write performance issue

[pdi]

Strange write performance issue after upgrading from ubuntu server x64 14.04 to 15.10.

Hdd's write speed is near 90-100Mb/s:
# dd if=/dev/zero bs=1M count=100000 of=/dev/sdb
Result: 102 MB/s

Checking write speed for simple LV:
# lvcreate -L 100g vghost -n lv1
# dd if=/dev/zero bs=1M count=100000 of=/dev/vghost/lv1
Result: 32.5 MB/s

And for LV + snapshot:
# lvcreate -L 100g -s vghost/lv1 -n snap1
# dd if=/dev/zero bs=1M count=100000 of=/dev/vghost/snap1
Result: 19.7 MB/s

Any ideas how to fix that?