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

[jd1008]

On 04/01/2015 10:40 PM, Robin Laing wrote:
> 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.
Good point. One burner is internal, the other is external.
My problem turned out to be the media, as you can see in my reply to g.

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