Creating large disk images in OS X
Here’s an observation about creating large disk images in OS X on the Mac using Disk Utility: it won’t work on FAT32 systems and the error message will be very strange.
Basically I created a 110 GB sparse disk image on an external harddrive and put a few GB of data on it. In the middle of copying data to it the disk image started to fail though, and in fact the whole image became corrupted and was unmountable.
The problem is that the external harddrive came factory formated for FAT32 which has a max file size of 4GB. So when the sparse image grew beyond that it broke.
Similarily if you try to create a normal disk image (not sparse) with a size greater than 4GB, you’ll get an error message. On my MacBook Pro running OS X 10.4.6 the error was ‘illegal seek’.
The solution was just to reformat the drive using the Mac’s own file system HFS+ which has a ridiculously large max file size (thousands of terabytes). After that you can go crazy with creating large disk images.
