Archived - MobileMe: Backup intended for backing up files in your Home folder, but not your entire startup disk
The Backup application, included with a MobileMe subscription, can be used to back up your important files. However, it is not intended to back up startup disks, Mac OS X installations, or your entire hard drive.
What kinds of backups is Backup intended for?
Backup is designed to back up personal data and settings that are in your Home folder, such as items on your desktop, preferences, iPhoto pictures, iTunes songs, your movies, and so forth. In other words, files you "own".
External disk or other (non-bootable) partition
You can use Backup to back up files you own that are on an external disk or other disk partition as long as the disk is not bootable (you can't start from it, that is). With Backup 3.2, this is determined by whether or not the hard drive has a /System folder at it's root level. Note that you must have permissions to the files you want to use Backup with. You can configure an entire volume (except your Mac OS X volume) to ignore permissions if you wish.
What kinds of backups is Backup not intended for?
Entire startup disk
Backup is not intended to back up applications or system files (files in /Applications, /System, /Library, and so forth), or your entire hard drive, because it runs with the same file permissions as the currently logged-in user. Not all files outside of a user's Home may be accessible. Similarly, Backup is not intended to back up a bootable Boot Camp partition.
Backing up items outside of your Home folder may appear to work, but the backup may not be successfully restored using Backup. If you want to check for specific files that may not have been backed up, check the backup.log file (open Console or System Profiler in /Applications/Utilties/ and click Logs).
A backup of your entire startup volume made with MobileMe Backup may not successfully back up, or may not be usable after restoring it.
Files in other user's Home folders
Because Backup runs with the same file permissions as the currently logged-in user, you can't use it for backup up files in other user account's Home folders even if they are on the same computer. Log in as the other user before using Backup.
With Mac OS X 10.5 Leopard or later, you can use use TimeMachine to back up your entire hard disk.