While trying to burn a 900mb ISO file on a dual layer DVD, I got the error. “more than 50% of space will be wasted! use single layer media for this recordiong”. I avoided it by burning a multi-session DVD (e.g.: growisofs -Z /dev/hdc -R -J /home/user/files/*). Another solution would be to add more files to the iso (using isomaster) until it is more then 50% of the capacity of a dual-layer DVD.

Debug output:

growisofs: 7.1
growisofs
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Executing 'builtin_dd if=/dev/fd/0 of=/dev/hda obs=32k seek=0'
:-( more than 50% of space will be *wasted*!
use single layer media for this recording
growisofs command:
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/usr/bin/growisofs -Z /dev/hda=/dev/fd/0 -use-the-force-luke=notray -use-the-force-luke=tty -use-the-force-luke=tracksize:437396 -dvd-compat -speed=2.4 -use-the-force-luke=bufsize:32m