Question about ISO files

[AMJF]

If I create an ISO file for a DVD, burn the ISO file to said DVD and then lose the ISO file, will I get exactly the same ISO file contents back if I create it from the burnt DVD? Or is there a difference in content?

 

[LIGHTNING UK!]

Sometimes drives will round up the number of sectors they burn to the nearest 16.

 

So if you read a disc with 14 sectors, you'll get an image with 14 sectors. Burn that 14 sector image to a disc and you may end up with a disc that appears to have 16 sectors and then when you read it back, you'll end up with an image with 16 sectors.

[AMJF]

Would explain a few things, like why there's a "size" and a "size on disk" for file size reports in Windows, eh?

 

Well, it's no effort to burn the disc and then recreate the ISO from the disc, it just takes time.

 

Thanks for the info, anyway

[dbminter]

You know?  I, too, have wondered for a while now what the bloody Hell's the difference between a file's "Size" and its "Size on disk." 

[AMJF]

It's been a while since I posted here, but I want to ask:

 

So sometimes if I do the above, there will be a difference in size, but basically, will all the data be the same, identical, on both ISO image and disc? And is it trailing zeroes that make up the difference? If so, that's not so bad and I can live with NOT recreating the ISO from the freshly-burned disc, but simply verifying the disc instead.

 

So will it be the same?

[LIGHTNING UK!]

Yes, when the drive rounds things up, it'll just pad the end with zeros. The actual data (files etc) will all be the same.