Re: [Bug-ddrescue] Best options for rescuing a DVD?

[Harri Järvi]

On 19.06.2011 09:38, Ian Oliver wrote:
> The third is different. I'm now in day 3 and have rescued 2471MB. I
> don't know how much data is on the disk: ddrescue went for all 4GB+ but
> I suspect that some sectors are missing at the start such that the size
> is unknown. Which driver/layer/device is responsible for determining
> size of tha DVD?

It is the responsibility of the block device subsystem of the kernel to 
determine the size of the block device.

You can query the block device size in bytes from the kernel by running 
the command

blockdev --getsize64 /dev/cdrom

Notice that the SCSI specification allows to report 75 of 2k-blocks more 
than the actual size. Thus, the block device subsystem may also report a 
bit too high a number. (drivers/scsi/sr.c)


--
Harri