I'm looking for ways to archive entire 9.1 GB hard drives to DVD media. I've seen advertisements for 9.4 GB media . First, I learned the "GB" in "9.4 GB" doesn't really mean the "gigabyte" we grew up knowing. We learned in math or science class that a kilobyte wasn't 1000 bytes. It was (note the "was" -- I'll explain below) 2^10, or 1024^1, or 1024 bytes. A megabyte was 2^20, or 1024^2, or 1,048,576 bytes. A gigabyte was 2^30, or 1024^3, or 1,073,741,824 bytes. According to the NIST Reference on Constants, Units, and Uncertainty , these definitions have changed: kilobyte = 1000 bytes megabyte = 1,000,000 bytes gigabyte = 1,000,000,000 bytes We have new terminology for the "prefixes of old": kibibyte (kiB) = 1024 bytes mebibyte (MiB) = 1,048,576 bytes gibibyte (GiB) = 1,073,741,824 bytes For example, discs advertised to be 4.7 GB are actually 4.7 billion bytes, or 4.37 "old GB." (Hard drive manuf