Information Technology Reference
In-Depth Information
•
Video:
If you download movies or TV shows regularly and then
delete them right after you watch them, you can save tons of space
on your backup drive by excluding the folder containing these files
(typically your
~/Movies
folder or a subfolder inside it). But do this
only
if you're sure you can download the movies again if necessary.
(Video purchased from the iTunes Store, for example, can be
downloaded again for free as long as they're still in Apple's catalog.)
(Sparse) Bundles of Joy
Mac OS X has long supported several disk image varieties, one
of which was the
sparse image
(extension
.
sparseimage
). Unlike
conventional disk images with a
.
dmg
extension, sparse images don't
have a fixed size; they can grow (up to a preset maximum size) as
their contents change. This helps avoid wasting space on your disk.
One type of disk image, the
sparse bundle
(which has the
extension
.sparsebundle
), looks and behaves almost exactly like
a sparse image, but with an interesting twist: behind the scenes,
this image is a bundle (hence the name) of smaller files called
bands
, each only 8 MB in size. As a result, when you modify files in
a sparse bundle image, only the band(s) used to store that particular
data change—and only those, much smaller, files need to be backed
up when Time Machine next runs.
Like sparse images, sparse bundles can be encrypted. To create an
encrypted sparse bundle:
1. In Disk Utility, choose File > New > Blank Disk Image.
2. Fill in the file name, location, volume name, and maximum size;
leave the format as Mac OS Extended (Journaled).
3. Choose either 128-bit or 256-bit AES encryption from the
Encryption pop-up menu. Leave Partitions set as it is.
4. From the Image Format pop-up menu, choose Sparse Bundle Disk
Image.
5. Click Create. Enter and verify a password and click OK.
Your new disk image appears in the designated location.
