When I use Disk Utility to create an image, it gives me five options:

  • Read only
  • Compressed
  • Read/Write
  • DVD/CD Master
  • Hybrid Image

Most of these make sense to me why someone would prefer one option over another option, except for Compressed. I tested it out and the Compressed option made my image nearly half the size of the uncompressed version, which is great.

Now, I don't know for sure by I am assuming that this Compressed format is either Read only or Read/Write and if this is the case, why would you ever choose one of those formats over Compressed?

I did not experience any loss of data when I did the Compressed and given the significantly smaller file size it seems like a no-brainer to always choose Compressed. Maybe I am making some wrong assumptions here...


When you create an image and you select Compressed, you are doing so at the sake of speed and read/write capability

To access the data on a compressed image, you have to uncompress it first; that takes cycles (cpu time). Secondly, per Apple, the image is read only, not read/write so you will lose that capability as well.

The "Compressed" format is great for archival of data, not for daily access.

  • 1
    It would be nice if apple changed "compressed" to "read-only (compressed)"
    – jerlich
    Jun 10 '20 at 4:19

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .