I'm actually coming around to Linux LVM - once you get the hang of the concepts and the associated commands it can be a straightforward exercise to extend your existing volumes after adding new physical disks. This differs from software RAID, as you have the ability to lay an LVM filesystem over a single disk and later take advantage of the LVM commands to resize your volumes if you so desire.
I recently was confronted with a VM that was out of space on /usr/local. The filesystem was already using LVM so I just added a new virtual disk and stretched the /usr/local volume over the new disk. The whole process is even easier in VMware as you can add the new disk while the machine is running and run through the whole process without a reboot, providing you don't have daemons or processes running in /usr/local that stop it from being unmounted. Here's how I did it:
init 1 umount /usr/local
Going to runlevel 1 may not always be necessary but was in my case. pvcreate enables the new physical disk for use with LVM. Then vgextend extends the volume group, and lvresze resizes the logical volume. In my case the new disk that was added became known to the system as /dev/sdc.
pvcreate /dev/sdc vgextend VolGroup00 /dev/sdc lvresize /dev/VolGroup/lvol0 -L 12.7G
Then use resize2fs to extend the file system into the free space. You are required to fun a filesystem check first.
e2fsck -f /dev/VolGroup/lvol0 resize2fs /dev/VolGroup00/lvol0 12700M mount -a init 3
In my example the previous size was 7.7Gb, I added a 5Gb disk and extended to 12.7Gb.
