Information Technology Reference
In-Depth Information
Full-Disk Encryption
FileVault 2, part of 10.7 Lion and later, can encrypt your entire
startup disk. Using Disk Utility, you can encrypt an entire external
disk too—select the disk and, in the Erase view, choose Mac OS
Extended (Journaled, Encrypted) from the Format pop-up menu.
(Obviously, this erases the disk; use appropriate caution.) If you
then use your favorite backup software to store a bootable duplicate
on that disk, you'll get an
encrypted
bootable duplicate!
Apart from FileVault 2, I'm aware of three software packages that
let you encrypt an entire Mac hard drive—internal or external—in
such a way that it remains bootable (if you have the password) and
are compatible with 10.8 Mountain Lion. (I still prefer Mac OS X's
built-in method, however.)
Sophos SafeGuard Disk Encryption for Mac
($60, volume discounts
available)
✦
Symantec Drive Encryption
($110 for individual copies, volume
discounts available)
✦
WinMagic SecureDoc for Mac
($118.80, volume discounts
available)
✦
Another option if you want to protect your data even if your backup
software itself doesn't offer encryption is to use a hardware-
encrypted drive. I list several of these in the
Online Appendixes
.
Delta Encoding
Until relatively recently, almost all Mac backup software performed
versioned backups on a file-by-file basis during incremental updates.
In other words, if just 10 bytes of a 10 GB file change, that marks the
file as modified, and thus the whole file must be copied on the next
backup run. Some software, however (such as Backblaze, CrashPlan,
QRecall, and even Mac OS X's Versions feature), have a capability
called
delta encoding,
which in earlier versions of this topic I referred
to as “sub-file incremental updates.” By whatever name, it means the
software can copy only the changed
portions
of files.
In some cases, the software copies only the individual
bytes
that have
changed since the last backup, and in other cases it copies larger units
