I recently bought a new Windows 7 operating system shipped on a DVD and wanted to make a backup copy of the disc. When I saved the contents of the DVD to my hard drive, the size of ISO file was exactly 3320903680 bytes.
After I burned the iso file to a DVD-R disc, I tested to make another ISO file from the DVD I just created. The size of the new ISO file was 3320905728 bytes so it was 2048 bytes more than what I expected. I also made a test by burning it to a DVD+R disc but the results were same.
Did I do something wrong? How can I burn a backup copy that would be exact the same as the original? Now if I would like to verify that the the burned DVD is correct, the hash would be different.
