Information Technology Reference
roll back to that state at a future time if the need arises. Taking
a snapshot saves the largest portion of your virtual disk in a read-
only state, so that as you continue to use the virtual machine in the
future, the changes are stored in smaller chunks that are quicker
to back up. In Fusion, you should also turn on AutoProtect to create
new snapshots automatically on a schedule. To do this, choose
Virtual Machine > Snapshots, click AutoProtect Settings, set
AutoProtect to On, and click Done.
Use backup software that supports delta encoding. If your
backup software copies only the changed portions of files, rather
than entire files (refer to Delta Encoding ), you needn't worry that
you'll have to copy 20 GB of data for every hour that you use
Back up virtual machines separately. You can exclude your
virtual machines from your regular versioned backups and then set
up a separate backup routine, just for the virtual machines, that you
run manually as needed—perhaps configuring your software to keep
only a limited number of backed-up versions in order to save space.
Warning! Before backing up a virtual machine using any Mac
backup software, make sure you pause, suspend, or shut down the
virtual machine. Otherwise, the disk image may change during the
backup process, leading to a corrupted and unusable backup.
If your Mac backup software creates versioned backups (whether
they're file-based or use delta encoding), an interesting consequence
of backing up a virtual machine is that the distinction between a
bootable duplicate and a versioned backup blurs. You have, in effect,
a versioned bootable duplicate—you can return your entire virtual
machine to its state at any previous time when a backup ran, although
you can't restore individual files or folders within your virtual machine
to earlier states independently. If that's important to you—as it well
may be—read on for how to create versioned backups of files and
folders from your Windows virtual machine.