lvextend extends the size of an LV. This requires allocating logical
extents from the VG's free physical extents. A copy\-on\-write snapshot LV
can also be extended to provide more space to hold COW blocks. Use
\fBlvconvert\fP(8) to change the number of data images in a RAID or
mirrored LV.

In the usage section below, \fB--size\fP \fISize\fP can be replaced
with \fB--extents\fP \fINumber\fP.  See both descriptions
the options section.