Mac OS X Leopard - ARCAism

Backup,
Synchronization, and
Recovery of Data
CHAPTER
Most people who have been around computers for a long time have horror stories of
disk crashes and data loss. And even if your story isn’t horrific, you probably have an
“Oh, $#!*!” moment or two when things go wrong and you lose an hour’s or a day’s (or more)
worth of work. The thing is, the minute your hard drive was created, it started a countdown
toward its mean time before failure (MTBF—a rating that measures the average amount of time
before a hard drive fails); in addition, we as people tend to occasionally make mistakes, so we
must make sure we have effective ways of backing up and syncing our data.
NOTE You can read an interesting article about drive failure from eWeek at www.eweek.com/
article2/0,1895,2099467,00.asp.
This chapter is dedicated to backing up and syncing data, not because it’s a terribly long and
complicated thing to explain (in fact, with the release of Leopard, it’s really relatively easy) but
because it’s such an important topic that it deserves to be treated on its own. In this chapter, we
will cover the following:
• The difference between backup and synchronization and what’s appropriate in what
circumstances
• Keeping your computer’s data backed up using Time Machine
• Syncing your data with iSync and .Mac
• Other methods of backup, syncing, and data recovery
The Difference Between Backups and
Synchronization
7
Before we go too far, it’s important to distinguish between a backup and a sync. In overly simple
terms, suppose you have two disks: disk A and disk B. If you back up disk A to disk B, you will
make an exact copy of disk A onto disk B, thus preserving all the data on disk A. If you synchronize
disk A with disk B, the information on each disk will be copied to the other, so each
disk will have the same information, which is the sum of disk A + disk B. One special type of
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