[linux-lvm] Why is part of a PV not usable?

["Allen, Jack" <Jack Allen mckesson com>]

Title: Why is part of a PV not usable?

Hello:
        When I do "vgdisplay -v" or pvdisplay to see the PV, why is part of the PV not usable?

 --- Physical volume ---
  PV Name               /dev/sdd1
  VG Name               vg01
  PV Size               10.00 GB / not usable 3.98 MB
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              2559
  Free PE               740
  Allocated PE          1819
  PV UUID               Q3LoGB-474h-ztit-HBA7-AUEX-OxpE-xoRo0J

-----
Thanks
Jack Allen