Confusion over LVM

[Andrew Wood <andrew@xxxxxxxxxx>]

Dear all,

I'm using FC6. I  have a 8 gbyte disk on my pc, and I've justed added 
another. Easy enough, ensuring the jumpers for master slave are set, etc.

I am a bit confused about the LVM. I used this, via the graphical front 
end to add the new physical volume. It looks like there are the two 
physical volumes, and two logical volumes - one of the logical volumes 
is uninitialised (swap I guess).

So, I thought that when one of the disks fills up then it would simply 
start allocating space on the new disk. However when I run the Software 
Updater then it terminates saying that there is insufficient space for 
them e.g.   [('installing package thunderbird-1.5.0.9-2.fc6 needs 13MB 
on the / filesystem', (9, '/', 12881920L)), ('installing package 
e2fsprogs-1.39-7.fc6 needs 14MB on the / filesystem' ...

I must have missed something, or do I have unfounded expectations of how 
LVM works (i.e. seemlessly)?

Andrew Wood, Oxford