Information Technology Reference
In-Depth Information
files look and act exactly like the originals. Another way is to copy
all the files into a single, larger file (sometimes called an archive file
or a backup set). Each approach has advantages and disadvantages.
Finder-format copies can be restored without backup software—just
drag and drop. Some people also feel more secure knowing they can
get at their files easily even if their backup software goes south. Of
course, the backed-up files generally take up exactly as much space
as the originals (Time Machine and Personal Backup store Finder-
readable files but avoid using extra space by using a Unix trick—see
the sidebar
The Magic of Hard Links
).
Archive files can be compressed as they're stored, potentially saving
a large amount of hard disk space. They can also be encrypted, so that
if your backup media were lost or stolen, no one could read your files
without knowing your passphrase. Of course, you will need the backup
software to restore files, and you could have a slightly higher risk of
data loss due to file corruption (since all the data is stored in a single
file)—but most backup software has verification mechanisms to
compensate for this.
Some backup software stores backups in disk images. Like archive
files, disk images can thus contain many files and folders—and can
optionally be compressed, encrypted, or both. But their contents are
also Finder-readable (assuming you have the passphrase, if any).
When making a duplicate onto another hard disk, Finder copies are
obviously mandatory; if you need an
encrypted
bootable duplicate,
you can either use full-disk encryption software—built into Mac OS X
and available separately from other vendors—or a hardware-encrypted
drive (see the sidebar
Full-Disk Encryption
, just ahead). For versioned
backups, I consider Finder-readable files optional—the benefits of
delta encoding and deduplication (discussed ahead), compression,
and encryption that you can often get with proprietary archive files
may outweigh the inconvenience of having to use backup software to
restore your data.
