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The best you can have is a sparse disk image, you set the maximum size that the image can be but it only takes up as much space as the contents and a little bit extra.

I just made a 200GB sparse disk image and the overhead with nothing in it is 110MBs, not bad at all.

To do this, open up "disk utility" in "utilities". Select "new image" and in the "image format" section select "sparse disk image"
 
The best you can have is a sparse disk image, you set the maximum size that the image can be but it only takes up as much space as the contents and a little bit extra.

I just made a 200GB sparse disk image and the overhead with nothing in it is 110MBs, not bad at all.

To do this, open up "disk utility" in "utilities". Select "new image" and in the "image format" section select "sparse disk image"

Thank you for the quick response. Let me get this right... I can create a 1TB disk image, but if the contents is only 10MB, then the space it takes up should be no more than 10MB?

Plus, in Leopard I see the option for a Sparse bundle disk image. What's the difference between that a normal Sparse disk image?
 
Thank you for the quick response. Let me get this right... I can create a 1TB disk image, but if the contents is only 10MB, then the space it takes up should be no more than 10MB?

Plus, in Leopard I see the option for a Sparse bundle disk image. What's the difference between that a normal Sparse disk image?

Well you have to take into account the overhead as illutstrated by my example, I just made a 1TB image and it takes 298MBs with nothing in (that is the overhead)

I don't know the answer to the second question, I created one and it has more overheads than just a normal sparse disk image and the Help menu isn't helpful at all.
 
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