I'm running several VMs with different versions of OS X in Parallels 11. In order to have a backup in case of a hardware failure, I got a second Mac and installed Parallels there as well, and then I copied the VMs from the old machine to the new one. When I started the VMs on the new machine, I was asked whether the VMs were copied or moved, and I replied that they were copied. Parallels changed the VMs' virtual Ethernet adapters' MAC addresses, as promised. It appears that it did not change the VMs' Hardware UUIDs, though (Apple -> About This Mac -> System Report -> Hardware -> Hardware UUID), and this is causing a problem backing up the VMs with Time Machine. I back up the VMs by running Time Machine *inside* the VMs, while putting the ~/Documents/Parallels folder on the host in Time Machine's exclude list. This way, I can control which parts of the VMs get backed up; I have significant exclude lists for Time Machine inside the VMs. The problem: it appears that Time Machine links backup images (sparsebundle files) on the AFP server to physical machines using the machines' Hardware UUIDs. The result is that my copied VMs and their respective originals are stepping on each other's Time Machine backups. Is there a way to get Parallels to reset the Hardware UUID on a guest, either to some value I provide, or some randomly generated value? All I found on the topic is this: http://kb.parallels.com/en/11197 but that appears not to work with Parallels 11.
