Pause VMs is the only realistic option. This is the correct option, because it ensures that guest is still alive. Other options might crash the guest, like Windows BSOD. Worse yet is that guest may think that it's hard disk is bad, and will start marking it's sectors as bad-blocks.
When the VM is paused, the user may take action to free some disk space and unpause guest manually. -- -Alexey Eremenko "Technologov"
