Why do I lose a large amount of space when using LVM?

Issue

• Disks appear to lose a large amount of disk space when using LVM.
• With 17.5 TB disk, LVM only shows 16.3 TB

# fdisk -l /dev/sdb
Disk /dev/sdb: 17967.7 GB, 17967781773312 bytes
255 heads, 63 sectors/track, 2184458 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

# pvdisplay /dev/sdb
  --- Physical volume ---
  PV Name               /dev/sdb
  VG Name               datavg01
  PV Size               16.34 TB / not usable 4.00 MB
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              4283852
  Free PE               786
  Allocated PE          4283066
  PV UUID               eHQF4F-yR3f-8FpR-P263-ZoJ5-W8j1-AYMRTg

• I created partition of 404GB, but f.s (no LVM) is only 365GB. What occupoes the extra 40GB?