DVD sizes and ISO/UDF



Hi everyone.

I have two questions, could you guys help me out?

  • I bought some blank DVDs, different brand and everything (like 4 different ones), and all of them say the capacity is 4.7 GB. So I was getting ready to burn some data with Nero, but oh surprise, seems like the max capacity is 4.38, whats up with that? I also tried with k3b on a linux box, and same thing. So why do they say the capacity is 3.8? Maybe 4.7 is only for DVD-Video format or something? Im really confussed, adn pissed off :slight_smile:

  • I tried to burn a 2.5 GB file on ISO mode with Nero, but it says I can only burn 2+ Gb files on UDF mode… so

[li]Besides UDF and ISO, there is UDF+ISO, which is used for DVD-Video if I got it right, but then I tried to burn the 2+ Gb file on such mode, and it keeps telling me it can ONLY be burnt on a UDF mode, not ISO, not UDF+ISO. So why do DVD movies are allowed to use UDF+ISO, and I cant. DVD-Movie discs differ on data-DVDs because they must contain some file structure (folders) and thats it, or am I missing something?
[/li][li]Using Ultra ISO or ISOBuster I analized the content of some Alcohol image (a backup I made of a movie), and the file format is ISO. So, why?? If the movie contains 2+ GB files, wasnt it supossed to be burnt with UDF mode??? (Or maybe Im crazy and there werent 2+ Gb files)
[/li][li]Same thing with alcohol, but this time, with a backup of a game. I double checked the original disc and the image, and yes, they contain some .CAB over the 2 GB limit, and well, the disc contains a ISO file system
So well, Im really confussed about this. Couldnt find much in the Nero help files or whatever, so thats why Im asking you guys.

Thanks a lot


Actually it is to do with the way numbers are counted, a Gb is counted as a thousand million bits when in fact it is not, 4.7Gb is only realy 4.38 as you have found out. Someone else can explain the maths better.


Me too … I tried to backup an MDF of 3.6 G.B from FAT32 Partition to Iso DVD but it said it is too large & I should use UDF DVD format instead .
Question now what is the difference between ISO & UDF File Systems?


iso and udf aren’t files systems they are file types, try searching there was a thread about different image types not that long ago.


You must use UDF FS. ISO/ or ISO/UDF only allow a max. filesize of 2GB.