Information Technology Reference
In-Depth Information
Items to Consider Excluding
Although you're free to let Time Machine back up as much or as little
as you want, I strongly recommend excluding the following items:
•
Virtual machine disk images:
Programs that let you run
Windows on your Mac typically store your entire Windows
installation in a special disk image file. These files can reach tens
of gigabytes, and since they change every time you run Windows,
Time Machine attempts to back them up with each run, bogging
down your Mac and wasting space on your backup disk. I suggest
excluding them from Time Machine and backing them up separately
(except as noted below):
‣
Parallels Desktop 6 and later stores virtual machines in such
a way that Time Machine need not back up the entire image
after its initial run—only the changed portions. If you're using
an earlier version of Parallels, however, you should exclude its
disk images, which are normally found in
~/Documents/Parallels/
name-of-virtual-machine
(the disk image files have an extension
of
.hdd
).
‣
VMware Fusion by default stores disk images in
~/Documents/
Virtual Machines
(with the extension
.vmwarevm
). Technically, the
file with the
.vmwarevm
extension is a package (a special folder
that looks and acts like a file); the actual disk image file inside
the package has an extension of
.vmdk
. But it's easiest to exclude
the entire
.vmwarevm
file.
‣
VirtualBox keeps its disk images in
~/Library/VirtualBox/VDI/
with an extension of
.vdi
.
•
Certain other large disk images:
Disk images (typically with
extensions
.dmg
or
.sparseimage
) serve many useful purposes,
such as providing a convenient way to package and distribute
downloadable software. You can also create your own disk image
using Disk Utility, optionally encrypting it so that all the files within
are protected with a password. However, most disk images you may
have created yourself, for whatever reason, have the same defect
