View Full Version : sparseimage vs dmg

08-31-2004, 12:13 PM
When cloning, SD! created a .dmg file. What is the difference between an .dmg file and a .sparseimage file, and when does SD! create one vs. another?

08-31-2004, 02:30 PM
Well, a .sparseimage is a file that can be mounted like any other disk, and will 'grow' based on the amount of data stored in it. So, a 30GB .sparseimage, when empty, may only be a few hundred K. As you place more data into it, it gets larger, until it reaches the maximum size set when it was created.

A .dmg is another kind of disk image. It's of a fixed size, and can be either read-only or read-write.

Page 20 of the manual goes into some detail about what SuperDuper! does when it directly creates an image -- that always results in a DMG, with a .sparseimage as an intermediate step. I recommend reading that page for additional ifnormation.

However, as described in this post (http://www.shirt-pocket.com/forums/showthread.php?t=81), you can use a sparse image directly to store backups in a "single file".

Hope that makes it clearer!