man lvcreate:
>        -L, --size LogicalVolumeSize[bBsSkKmMgGtTpPeE]
>              Gives the size to allocate for the new logical volume.  A size suffix of K for kilobytes, M for megabytes, G for gigabytes, T for terabytes, P for petabytes or E for exabytes is optional.
>              Default unit is megabytes.