question about burning and then reading (dd) to confirm sha256sum

[Robin Laing]

On 2015-04-01 19:15, g wrote:
>
>
> On 04/01/2015 02:18 PM, jd1008 wrote:
>> After burning 3 DVD's, and reading them back to compute sha256sum.
>> all three of them generated these error messages during readback,
>> and all 3 messages show the error was past the 4gb offset.
>>
>> Is this a media issue or is it the burner?
>
> 1- burn dvd at 2 speeds lower than what you used and had failure.
>
> if ok, problem is either burner or blanks.
>
> 2- burn dvd at failure speed on a different burner.
>
> if ok, get a new burner. if failure, may be blanks.
>
> 3- try different program or burn from command line.
>
>> A side question: why does the block io layer assume that all media
>> have 512 byte sectors?
>
> i believe that is a carry over from disk formatting started by the
> IBM PC. [do not hold me to that]
>
>

Also watch power supply voltages.

I have ran into two power supplies that caused issues with CD burning. 
Couldn't supply that little extra bit of current during the burn 
process.  To burners later, I finally found it.