why doesn't "df" show a larger logical volume?

["Robert P. J. Day" <rpjday mindspring com>]

  in prep for trying to install oracle on my FC2 system, i used
"lvextend" to extend one of my logical volumes by a few gig.  but when
i mounted it again (did i have to unmount it first?), "df" showed me
the same output as before.

  should i have expected "df" to show me a larger 1K block value?  now
"lvdisplay" shows me:

  LV Name                /dev/vol0/archive
  VG Name                vol0
  ...
  LV Size                14.00 GB   <-- looks good

but "df" shows me:

                      1K blocks  Used       Avail
/dev/mapper/vol0-archive
                      10321208   2336136   7460784  24% /archive
                      ^^^^^^^^ ??

so where'd my extra 4G go?  and should i assume it's just going to
show up when oracle dumps a 10G footprint on my system?

rday