Information Technology Reference
In-Depth Information
Virtualization Software
If you use virtualization software such as Parallels Desktop or VMware
Fusion, your Windows files live on a special disk image that appears as
a regular volume in Windows. Your existing Mac backup software can
copy that disk image, making what amounts to a bootable duplicate
of your virtual machine—but read on to learn about some potential
pitfalls of doing so. You can also use any of several techniques to make
versioned backups of individual files and folders inside your virtual
machine, either in Mac OS X or from within Windows.
Duplicate a Virtual Machine
Since a virtual machine disk image is, as far as Mac OS X is concerned,
merely a file (or, in some cases, a series of files), the easiest way to
back them up is simply to ensure that your Mac backup software copies
them along with the rest of your documents. In other words, whether
you create a duplicate or a versioned backup of your Mac data, you still
end up with a bootable duplicate of your Windows virtual machine.
But there's a catch. The disk image is usually quite large—often in the
tens of gigabytes. And, simply running Windows modifies the image.
That creates a problem for any backup software that does file-by-file
incremental updates (as Time Machine does, for example), because
it will consider the whole file to have changed each time. Adding these
disk images to versioned backups will rapidly chew up disk space, and
make backups take much longer.
You can solve this problem in any of several ways:
Use Parallels Desktop 6 or later. Starting with version 6,
Parallels stores its disk images as a set of much smaller files, and
unlike VMware Fusion (which can also split virtual disks into
smaller segments), Parallels ensures that as few segments as
possible are changed each time it runs. That means that Time
Machine and other file-based backup programs won't bog down
during each incremental update.
Create snapshots. Both Parallels and Fusion let you take
snapshots of your virtual machine's current state, so you can
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