Lvm – Why does the lvm physical volume have significantly less space than the partition it contains

I'm on centOS 6.4.
I have a 39TB hardware RAID configured as RAID 6.
I created a single 39TB partition with parted. It reports:

(parted) print                                                        
Model: JetStor JetStor -VOL#000 (scsi) Disk /dev/sdb: 39.0TB Sector
size (logical/physical): 512B/512B Partition Table: gpt
Number  Start   End     Size    File system  Name     Flags  1     
1049kB  39.0TB  39.0TB               primary

I created an lvm linear volume like so:

pvcreate /dev/sdb1
vgcreate vg_jet716s /dev/sdb1
lvcreate -L 30T -n lv_jet716s_1 vg_jet716s

Then I created an XFS fs on lv_jet716s_1, matching the raid stripe width and number:

mkfs.xfs -d su=64k,sw=13 /dev/mapper/vg_jet716s-lv_jet716s_1

But pvs outputs this:

[root@cfile ~]# pvs   PV         VG         Fmt  Attr PSize   PFree   
/dev/sda2  vg_cfile   lvm2 a--  464.76g 285.62g
/dev/sdb1  vg_jet716s lvm2 a--   35.47t   5.47t

I don't think I checked what pvs was outputing after creating just the physical volume. I probably only called 'lvs' to see that the logical volume had been created witht the right size. Here's lvs and vgs:

[root@cfile ~]# lvs
  LV           VG         Attr      LSize  Pool Origin Data%  Move Log Cpy%Sync Convert
  lv_root      vg_cfile   -wi-ao--- 50.00g                                             
  lv_swap      vg_cfile   -wi-ao--- 31.48g                                             
  lv_var       vg_cfile   -wi-ao--- 97.66g                                             
  lv_jet716s_1 vg_jet716s -wi-ao--- 30.00t                                             
[root@cfile ~]# vgs
  VG         #PV #LV #SN Attr   VSize   VFree  
  vg_cfile     1   3   0 wz--n- 464.76g 285.62g
  vg_jet716s   1   1   0 wz--n-  35.47t   5.47t

Any thoughts? I'm new to this and it's really surprising to lose almost 10% of my space. Thanks!

-Michael