Could you ensure me that minimal LVM2 size Unit is one extent to which all sizes are rounded up ?Is 4MiB the default size of extent for LVM2 ?Can it be configurable or is it the only size ?Small experiment of try of creating 2B logical volume:# lvcreate -L 2 r2Ta -n test2b  Rounding up size to full physical extent 4.00 MiB                                                                                                                       Logical volume test2b created# lvdisplay /dev/mapper/r2Ta-test2b  | grep 'LV Size'                                                                                             LV Size                4.00 MiB 
What is the smallest LVM2 logical volume unit?
partition;storage;lvm
Yes, the minimum size is one physical extent.  You can specify the PE size when you create the volume group with the -s switch to vgcreate.