6.7. Insufficient Free Extents for a Logical Volume

You may get the error message "Insufficient free extents" when creating a logical volume when you think you have enough extents based on the output of the vgdisplay or vgs commands. This is because these commands round figures to 2 decimal places to provide human-readable output. To specify exact size, use free physical extent count instead of a multiple of bytes to determine the size of the logical volume.
The vgdisplay command, by default, includes this line of output that indicates the free physical extents.
# vgdisplay
  --- Volume group ---
  Free  PE / Size       8780 / 34.30 GB
Alternately, you can use the vg_free_count and vg_extent_count arguments of the vgs command to display the free extents and the total number of extents.
# vgs -o +vg_free_count,vg_extent_count
  VG     #PV #LV #SN Attr   VSize  VFree  Free #Ext
  testvg   2   0   0 wz--n- 34.30G 34.30G 8780 8780
With 8780 free physical extents, you can enter the following command, using the lower-case l argument to use extents instead of bytes:
# lvcreate -l 8780 -n testlv testvg
This uses all the free extents in the volume group.
# vgs -o +vg_free_count,vg_extent_count
  VG     #PV #LV #SN Attr   VSize  VFree Free #Ext
  testvg   2   1   0 wz--n- 34.30G    0     0 8780
Alternately, you can extend the logical volume to use a percentage of the remaining free space in the volume group by using the -l argument of the lvcreate command. For information, see Section 4.4.1, “Creating Linear Logical Volumes”.