How to resolve the Insufficient Free Extents for a Logical Volume in Linux Server?

 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 this commands round figures to 2 decimal places to provide human-readable output. To specify exact size, use free physical extent count instead of some 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.

[root@tng3-1 ~]# 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 run the following command, using the lower-case l argument to use extents instead of bytes:

# lvcreate -l8780 -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.