Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Isn't it the case that a DVD can only hold at most 4.7G of data? How can Apple fit these data into a DVD?

I discovered it when I tried to restore the install disk image to a USB flash drive.

share|improve this question
up vote 5 down vote accepted

Quoting Wikipedia...

Dual-layer recording (sometimes also known as double-layer recording) allows DVD-R and DVD+R discs to store significantly more data—up to 8.54 gigabytes per disc, compared with 4.7 gigabytes for single-layer discs.

share|improve this answer
+1 - Dual-Layer vs. Single-Layer is it. – afrazier Jun 14 '11 at 14:08

These are special types of DVD's. You see it sometimes when you try to rip a film from a DVD. There are DVD's wich hold more than 4,7GB of data. Because 4,7GB is not enough, or otherwise to prevent the DVD from being copied. I've also got an old PC-game of Rayman here, wich is just a CD (it works in a CD-ROM-drive wich can't read DVD's, so no, I'm not mistaken), except that it holds 2,2GB of data.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.