3.7   Creating CD and DVD Backups

By combining DropDMG’s imaging and burning features, you can easily backup your files to CD-R/RW or DVD-R/RW. DropDMG will store the files efficiently on the discs, and you can optionally protect them using encryption.

1. First, open DropDMG’s Preferences window and set the options that you want to use for the backup. Probably you want one of the compressed .dmg formats. If you want the backup to be encrypted, enter a passphrase. Check Limit segments to at most __ MB and enter the size of your backup discs, e.g. 680 MB for a typical CD or 4450 MB for a DVD. Uncheck (or set to None) all the items in the Options section of the window. In the Save section, choose a destination folder where the image should be saved and (if you want) choose Append Current Date from the Name Processing menu. You may want to save these settings as a Configuration so that it’s easy to recall them the next time you make a backup.
2. To backup a folder, drag it onto DropDMG’s status window. DropDMG will create one or more .dmg and .dmgpart files that contain the contents of the folder. You should not modify the contents of the folder while DropDMG is creating the image.
3. To burn a .dmg or .dmgpart file to disc, choose Burn Folder/File… from DropDMG’s File menu or Shift-Option-drag the file onto DropDMG’s status window.
4. After the burning is complete, you can delete the .dmg and .dmgpart files that you burned.

Although this simple backup method will not meet everyone’s needs, it does have a variety of advantages over ultra-simple backup methods (e.g. Burn Folders in the Finder) and more specialized backup software (e.g. Retrospect):

• Collecting the files onto a .dmg file is better than burning the files directly. The .dmg file can be compressed (to save space) and encrypted (so you can keep your off-site backup private). It contains a checksum so that if the disc ever gets damaged, you’ll know. Finally, you can easily backup large files that don’t fit on a single CD or DVD because DropDMG will save them into disc-sized .dmgpart files.

• Backups created with DropDMG are stored in a standard Mac OS X format. The software needed to restore them is built into the operating system.

• DropDMG’s seemingly inefficient two-step process (creating the image files and then burning them) can actually save you time. If you were using Retrospect to backup a large folder, it would prompt you for discs as it copied the files. Then, when it was done, it would prompt you for all the discs again to verify them. During this time, you would not be able to modify the files in the folder, because the backup could be corrupted if you modified files that were in the midst of being copied. Thus, the amount of time that your Mac is “out of commission” is determined by the time it takes to do the burning and swap all the discs.

  With DropDMG, the first step of creating the .dmg files can run unattended, while you’re at lunch or sleeping. When you get back to your Mac, you can burn the files to disc at your leisure. Since the folder has already been “snapshotted” to the disk image, you can access and modify the folder while burning the discs. Furthermore, if you have multiple optical drives you can save time by burning multiple discs at a time. Since each disc is verified individually, right after it’s burned, you don’t have to swap the discs twice.