The latest versions of Parallels Desktop include improved integration with Time Machine. Per kb 8827 "When your virtual machine is backed up, only the most recent changes are saved (the latest snapshot), so the backup process takes less time and uses less space on your Time Machine storage device." On the other hand, the current Parallels Desktop User's Guide contains this warning: "Warning: Time Machine backups can guarantee safety only when your Parallels virtual machines were stopped or suspended during the backup." Does this mean that if Time Machine makes a backup while virtual machines are running, the backup could be corrupt and totally useless?
Hi WinL, it is always recommended to backup using Time Machine when the virtual machine is not in use. We suggest you to setup the backup, whenever your virtual machine is in shut down mode.
Thanks Dhruba, Unfortunately Apple doesn't provide a way to schedule Time Machine backups, it will run whenever it wants to. Third party tools are available for scheduling backups if you want to use Time Machine, but that's not an ideal solution either. An ideal solution would be for Apple to provide a way to defer Time Machine backups while a given process (like parallels) was executing. For now, the best approach is to select the "Do not backup with Time Machine" check box and back the virtual machines up by drag and drop to an external drive.
Ahhh...There is a way to defer Time Machine while Parallels Desktop is running, it can be done with a shell script and a few tools. There is a command line tool that will disable and enable Time Machine backups (tmutil). A shell script can be written to disable Time Machine, start Parallels Desktop on a virtual machine using the open command with the wait option (an Xcode command line tool does this), finally enable Time Machine when Parallels Desktop quits (the wait returns). It's kind of a kludge but it more or less works. The point of this is that if a kludge can be put together with a few command line tools, he who has the source code to Parallels Desktop can probably implement a much more robust solution, it's not that everyone should use the kludge that's described here.
Also, it is not advisable to back up the virtual machine while running even if it is possible to back it up. Also, Time machine is an incremental based backup method. Still, we will share your feedback with the concerned team.
