Using Time Machine with Virtualization (Parallels, VirtualBox, VMWare, etc...) Since a single small change to a VM file should (I think) cause the entire multi-gigabyte file to be backed up again, are there any ideas I can use to more effectively backup my machine?

Assume that I only need one copy of a VM, and changes made to the VM don't matter.

For example:


Backup the VM using time machine once, then exclude the folder that contains all the VMs
Exclude the VM's altogether and manually back up the VMs
Let Apple's software do it's thing, it will be effective at managing the disk space
Parallels has a specific setting to optimize its VMs for backup by Time Machine and prevent backing up unchanged data.


  To enable improved integration with Time Machine, please go to Virtual Machine Configuration, choose Options and hit Backup.
  
  Select "Optimize for Time Machine" in SmartGuard menu.


Similarly, VMWare Fusion has some support for Time Machine, which appears to involve turning on snapshots.