I'm a bit unclear on your setup. The disk is a file on the host machine, and the VM is using LVM for it's partitioning, correct?
So you should be able to increase size of the disk file (using whatever procedure is correct for your virtualization setup) then inside the VM it should look like the hard disk magically grew. You may be able to do a pvresize and have the physical volume resize to take up the extra space. Then your volume group should be bigger, and you can resize logical volumes or add new LVs as needed.
I once added a drive to a RAID and expanded the size of the array, so I used pvresize to expand and use the whole space.
If I'm misunderstanding your setup, please clarify. I'm not sure why you'd what to reduce the size of the LV.
Last edited by Gomer_X; 01-04-2012 at 05:21 PM.