Hi,
For the second disk look here: http://forum.proxmox.com/threads/7782-how-i-can-move-all-VMs-to-a-2nd-HDD
and to move do an shutdown of VM; backup (via gui); restore via cli (qmrestore) and use the option --storage "storagename-of-disk" to restore the VM-disks on the second disk.
Of course you need the space for backup (you can also copy directly with dd but should know what you are doing).
Thanks & I am assuming the same applies if I decide to install a fresh install proxmox in a brand new server and move that VM to that new server and do a restore will the VM boot up - like how it was working in my older machine ?